General Chemistry Questions TPR
Galvanic Cell Voltaic Cell Corrosion Cell Spontaneous Cell
- A spontaneous redox reaction to generate an electric current. - Anode is oxidized (an ox). - Cathode is reduced (red cat). - Electrons travel from the anode to the cathode.
Electrolytic Cell Nonspontaneous Cell
- An external voltage source creates an electric current that forces a nonspontaneous redox reaction to occur (electrolysis). - Anode leaves as a gas. - Cathode accumulates.
How can acidic salts be identified?
- They are weak acids. - No Group I or II cations are acidic.
How can basic salts be identified?
- They are weak bases. - Cl-, Br-, and I- are never basic.
Given the enthalpies of formation for NO and NO2 are 90 kJ/mol and 33 kJ/mol, respectively, what is the reaction enthalpy for 2NO (g) + O2 (g) --> 2NO2 (g)?
-114 kJ/mol
What change in the equilibrium constant results from changing pressure when there is a different number of moles of gaseous products than reactants?
-Reduced volume, increased pressure, shifts towards side with fewer moles of gas. -Increased volume, decreased pressure, shifts towards side with more moles of gas.
van der Waals Equation
-a and b are specific to individual gases. -a accounts for intermolecular forces. -b accounts for particle volume.
Convert from atm to pascals
1 atm = 101,300 Pa
Convert from atm to mm Hg
1 atm = 760 mm Hg
Convert from atm to torr
1 atm = 760 torr
Standard Temperature and Pressure (STP)
1 atm and 0 degrees Celsius
What are the 2 criteria for creating hydrogen bonds?
1. A molecule must have a covalent bond between H and either N, O, or F. 2. Another molecule must have a lone pair of electrons on an N, O, or F atom.
What are 2 ways to increase the rate constant for a given reaction?
1. Add a catalyst to reduce activation energy. 2. Increase temperature.
Salt Solubility Rules
1. All Group I and ammonium salts are soluble. 2. All nitrate (NO3-), perchlorate (ClO4-), and acetate (C2H3O2-) salts are soluble. 3. All silver (Ag+), lead (Pb2+/Pb4+), mercury (Hg2 2+/Hg 2+), carbonates (CO3 2-), phosphates (PO4 3-), and sulfurs (S 2-) are insoluble except for their nitrates, perchlorates, and acetates.
What are 5 similarities between Galvanic and Electrolytic cells?
1. Anode is oxidized. 2. Cathode is reduced. 3. Electrons flow from anode to cathode. 4. Anions migrate to anode. 5. Cations migrate to cathode.
What 3 rules are used to explain electron configuration?
1. Aufbau principle. 2. Hund's rule. 3. Pauli exclusion principle.
What are 3 types of beta decay?
1. Beta - Decay. 2. Beta + Decay. 3. Electron Capture.
What are 6 factors that influence reaction rate?
1. Collision frequency. 2. Reactant concentration 3. Molecular orientation. 4. Kinetic energy. 5. Temperature. 6. Activation energy.
What phase changes release heat?
1. Condensation. 2. Freezing. 3. Deposition.
What are the 4 quantum values for an atom?
1. Energy shell (n). 2. Energy sub-shell (s, p, d, f). 3. Orbital orientation. 4. Electron Spin (up or down).
What are 4 differences between Galvanic and Electrolytic cells?
1. Galvanic cells spontaneously generate electric power. Electrolytic cells require an external power source. 2. Galvanic cells have a positive total Enaught. Electrolytic cells have a negative total Enaught. 3. Galvanic anion is negative. Electrolytic anion is positive. 4. Galvanic cathode is positive. Electrolytic cathode is negative.
What are 4 physical properties that are altered with increased intermolecular forces?
1. Greater melting points. 2. Greater boiling points. 3. Greater viscosities. 4. Lower vapor pressures.
What are the 6 most common strong acids?
1. HI, Hydroiodic acid. 2. HBr, Hydrobromic acid. 3. HCl, Hydrochloric acid. 4. HClO4, Perchloric acid. 5. H2SO4, Sulfuric acid. 6. HNO3, Nitric acid.
What conditions encourage ideal gas behavior?
1. Higher temperatures. 2. Weakest intermolecular forces. 3. Smallest molecular weights. 4. Low pressure.
What phase changes absorb heat?
1. Melting/Fusion. 2. Vaporization. 3. Sublimation.
How is solubility affected by temperature?
1. The solubility of solids in liquids increases with increased temperature. 2. The solubility of gases in liquids tends to decrease with increasing temperature.
What percentage of HF (pKa = 3.17) dissociates in one liter of solution containing two moles of the acid?
1.8%
What information does 1/2 the equivalence point give?
1/2 equivalence point = pKa
What is the slope in a phase transition diagram equal to?
1/C (heat capacity, or mc)
What is Faraday's constant?
96,485 C/mol e-
Arrhenius Equation
A accounts for the orientation of the colliding molecules. R is the gas constant 0.0821 L-atm/K-mol.
Solubility Product Constant Ksp
A value for the extent to which a salt will dissolve in water at equilibrium.
H2 is removed from an electrochemical cell in which metallic magnesium is oxidized, and H+ is reduced. At STP the volume of gas is measured to be 11L. If the reaction has proceeded for 2 hours at constant current, what was the value, in amps, of the current? A) 13.4 B) 6.5 C) 3.2 D) 19.9
A) 13.4 At STP, 1 mole of gas occupies 22.4L. Production of 1 mole of H2 requires 2H+ and 2e-.
LOOK AT THE OTHER SIDE OF THIS FLASHCARD FIRST The important thing to notice about this graph is the labeling of the axes. Although most titration graphs have a y-axis of pH, this one is pOH. This means that the shape that would normally indicate that a weak acid was being titrated by a strong base ACTUALLY indicates that a weak base is being titrated by a strong acid. Lastly, pKb is the y-value (since it's in terms of pOH) of the half-equivalence point (about 4.2).
A) A weak acid is being titrated by a strong base, and this acid has a pKb of 4.2. B) A weak base is being titrated by a strong acid, and this base has a pKb of 4.2. C) A weak base is being titrated by a strong acid, and this base has a pKa of 4.2. D) A weak acid is being titrated by a strong base, and this acid has a pKa of 4.2
Which of the following pairs will generate an electrolytic cell with the least stable products? Al^3+ + 3e- --> Al(s) _________E = -1.68V Cd^2+ + 2e- --> Cd(s)________E = -0.40V Ag^+ + e- --> Ag(s)___________E = 0.80V Br2(l) + 2e- --> 2Br^-_________E = 1.08V A) Al^3+ and Ag(s) B) Br2(l) and Al(s) C) Cd2+ and Br- D) Ag+ and Cd(s)
A) Al^3+ and Ag(s) The electrolytic cell with the most negative electrical potential will have the least stable products. Find the potential by subtracting the oxidative E value from the reduction E value. Thus -1.68 - 0.80 = -2.49
Step 1: NO + Br2 --> NOBr2 (Fast) Step 2: NOBr2 + NO --> NOBr (Slow) A chemist determines the rate law of the overall process above to be rate = k[NO][Br2], which seems inconsistent with the mechanism. What best explains her findings? A) An inhibitor was present which affected the first step in the mechanism. B) Catalysis of the first step in the mechanism occurred. C) An increased quantity of Br2 was added to the system. D) An increased quantity of NO was added to the system.
A) An inhibitor was present which affected the first step in the mechanism. The chemist finds the first step is now dictating the overall reaction rate. One possible explanation would be the inhibition of the first step, causing it to become the rate determining step. Catalysis of the first step and increasing reactant concentrations would only further increase the rate of the first reaction, leaving the second step as the rate determining step.
The mean free path length (l) of a gas molecule is the average distance it will travel between collisions with other molecules. If l is directly proportional to T/P, which of the following is true? A) At a given pressure, molecules with higher kinetic energy have a longer l. B) At constant temperature, higher pressure leads to a longer l. C) Decreasing the volume of a sample at constant T will lead to a longer l. D) The length of l for atmospheric gases is, in general, shorter at high altitudes.
A) At a given pressure, molecules with higher kinetic energy have a longer l. Kinetic energy is proportional to temperature, thus high kinetic energy means high temperature.
A 44.8L container is filled with 1 mole of ideal gas X and 1 mole of real gas Y at 0C. The pressure inside the container is A) Between 0.5 and 1 atm. B) 0.5 atm. C) less than 0.5 atm. D) 1 atm.
A) Between 0.5 and 1 atm. Since gas Y is a real gas, its molecules experience intermolecular forces resulting in less force exerted on the walls of the container. The partial pressure exerted by the real gas is less than its ideal partial pressure. Therefore, the total pressure is 0.5 atm from ideal gas X plus something less than 0.5 atm from real gas Y, making the total pressure between 0.5 atm and 1 atm.
Which of the following compounds is a weak electrolyte? A) CH3COOH B) CH3OH C) BaCl2 D) KOH
A) CH3COOH Strong electrolytes dissociate into ions when dissolved in water. Weak electrolytes partially dissociate in solution. KOH and BaCl2 are strong electrolytes because they are ionic compounds. CH3OH does not dissociate, so it is not an electrolyte, leaving A as the correct answer.
Which of the following statements is true concerning a solution of H2CO3 at 25C? A) Decreasing the pressure of CO2 above the solution will decrease the acidity of the solution. B) Increasing the temperature will increase the acidity of the solution. C) The pKb of HCO3- is greater than the pKa of HCO3-. D) The Kb of H2CO3 is greater than 1 x 10^-7.
A) Decreasing the pressure of CO2 above the solution will decrease the acidity of the solution. The solubility of a gas in a liquid decreases with decreasing pressure. Reduced pressure would cause CO2( g) to escape from solution and the equilibrium would shift left causing there to be less H2CO3.
Which pair of liquids below will be immiscible? A) H2O and CCl4 B) CH3OH and CH3CH2OH C) CH3CH2CH2CH2CH3 and CH3CH2CH2CH2Br D) CCl4 and C6H6
A) H2O and CCl4.
Given starting conditions of -100C and 1 atm, which of the following changes could potentially result in CO2 fusion? A) Increased pressure and increased temperature. B) Increased pressure and decreased temperature. C) Decreased pressure and increased temperature. D) Decreased pressure and decreased temperature.
A) Increased pressure and increased temperature. In order to pass from the solid phase into the liquid phase, both temperature and pressure would have to be increased.
Given that the self-ionization of water is endothermic, what is the value of the sum pH + pOH at 50 degrees Celsius? A) Less than 14. B) Equal to 14. C) Greater than 14. D) Cannot be determined.
A) Less than 14. This is a Le Chatelier's principle question in disguise. Since the reaction is endothermic, heat is considered to be one of the reactants. Thus adding heat will push the reaction towards ionization, causing pH and pOH to both be lower than 7, so their sum will be less than 14.
Addition of which of the following salts will most likely result in a precipitate when mixed with an aqueous solution of AgNO3? A) NaCl B) Mg(ClO4) C) Hg(NO3)2 D) NaCH3COO
A) NaCl Most Ag+ compounds have low solubility in water. According to solubility rules, exceptions should include nitrates, acetates, and perchlorates. The addition of NaCl would result in the formation of AgCl, a water insoluble compound that would immediately precipitate.
Rechargeable batteries such as NiCad or lead-acid batteries can operate as both galvanic cells during the discharge cycle, or as electrolytic cells during the recharging cycle. Which one of the following statements accurately compares and contrasts these two cycles? A) Oxidation takes place at the positive electrode during recharging, but oxidation takes place at the negative electrode during discharging. B) Reduction takes place at the anode during recharging, but reduction takes place at the cathode during discharging. C) Oxidation takes place at the anode during recharging, but oxidation takes place at the cathode during discharging. D) Reduction takes place at the positive electrode during recharging, and oxidation takes place at the negative electrode during discharging.
A) Oxidation takes place at the positive electrode during recharging, but oxidation takes place at the negative electrode during discharging. Oxidation always occurs at the anode and reduction always occurs at the cathode, but the sign of the anode and cathode are reversed in galvanic and electrolytic cells.
Enough HF (Ka 7.4 x 10^(-4)) is added to water to create a pH = 2.1 solution. The addition of which of the following would have the least impact on the pH of this solution? A) PbF2 B) NH4F C) Na2CO3 D) NaF
A) PbF2 PbF2 is essentially insoluble in water, and therefore will have the least affect on the pH. Both NaF and NH4F are soluble salts, and will decrease the solubility of HF due to the common ion effect (eliminate B and D). Na2CO3 is a soluble salt and CO3^2- is the conjugate base of a weak acid, so it will increase the pH.
If an atom's atomic number equals its atomic weight, which of the following would be true? A) The number of protons equals the number of electrons. B) The number of neutrons equals the number of protons. C) The number of neutrons equals the number of electrons. D) The number of protons is less than the number of neutrons.
A) The number of protons equals the number of electrons. The only scenario in which this can occur is if the atom does not contain any neutrons. Thus, for a neutral atom, the number of protons must equal the number of electrons. This is the least wrong answer.
A chemist seals a rigid reaction vessel containing a gaseous reaction at equilibrium and begins pumping in helium gas. She fails to see a change in the relative quantity of reactants and products in the system of study. Which of the following best explains these observations? A) Total pressure has increased with no change in the reaction quotient. B) Total pressure has increased with compensatory changes in Q and Keq. C) Total pressure has decreased with no change in the reaction quotient. D) Total pressure has decreased with no change in the reaction quotient.
A) Total pressure has increased with no change in the reaction quotient. Sealing a rigid container and adding gas will increase pressure (C and D are wrong). Addition of an inert gas results in a decrease in the mole fraction for each gas in the mixture, but no change in partial pressures and therefore no change in Q. Also, changing reactant or product concentrations cannot change Keq, only a change in temperature can.
When CaF2 is added to a 0.02 M solution of NaF, the solubility of CaF2 is: A) low, because the concentration of F- already present in solution prevents dissolution of CaF2. B) unaffected by the presence of sodium fluoride. C) low, because less water is available for solvation due to the presence of NaF. D) high, due to the common ion effect.
A) low, because the concentration of F- already present in solution prevents dissolution of CaF2. The addition of dissolved F- decreases the solubility of CaF2. This is the common ion effect. why? Ca has 2+ charge while Na is 1+, so less stable despite larger size?
Phase changes that spread molecules out __________ heat.
Absorb.
What is another name for transition state?
Activated Complex
How is a cell's voltage determined?
Add the standard reduction potential for the reduced species with the negative of the oxidized species' potential.
How is pH calculated with weak acids?
After using the "ICE box" method, this formula will be used to calculate pH with weak acids.
What are the 3 types of decay?
Alpha, beta, and gamma.
What is the difference between anions and cations?
An anion is a negatively charged ion. A cation is a positively charged ion.
In a galvanic cell, which component is oxidized and which is reduced?
Anode is oxidized Cathode is reduced. (An ox; red cat)
Given the Nernst equation below, solve for Keq for the oxidation-reduction reaction Zn + Cu^2+ --> Zn^2+ + Cu where Enaught = 1.10V E = Enaught - (0.059V/n)logQ A) 1 x 10^37 B) 1 x 10^19 C) 1 x 10^-37 D) insufficient information provided
At equilibrium, the electrical potential for a cell is equal to zero and Q = Keq. n = 2 because 2 electrons are transferred during the redox reaction.
What is the significance of the half-equivalence point in redox titrations?
At the half-equivalence point, E = Enaught.
A 2 M solution of the potent organic pollutant sodium methylthiolate (NaSCH3) is titrated to its endpoint with 2M HCl. Which of the following best approximates the pH of the resultant solution? (pKb of SCH3- = 3.6) A) -log (2 x 10^{-5.2}) B) -log (1 x 10^{-5.2}) C) -log (1 x 10^{-1.8}) D) -log (1 x 10^{-3.6})
B) -log (1 x 10^{-5.2}) Although the solution initially started at 2M, after titration with another 2M solution, assume the concentration of NaSCH3 is halved, therefore 1M is used in the ice-box.
The Ka of formic acid is 1.8 x 10^(-4). What is the pKb of the formate ion? A) 14 - log(1.8 x 10^(-4)) B) 14 + log(1.8 x 10^(-4)) C) -14 + log(1.8 x 10^(-4)) D) - 14 - log(1.8 x 10^(-4))
B) 14 + log(1.8 x 10^(-4)) For a conjugate pair, such as formic acid and the fomate ion, the product of the Ka of the acid and the Kb of the base is equal to 10^(-14). The equation KaKb = 10^(-14) is equivalent to the equation pKa + pKb = 14. Therefore, pKb = 14 - pKa.
A 40g sample of argon (mw = 39.9) at 760 mm Hg and 25C is cooled to 0C. What is the final volume of this sample? A) 11.2L B) 22.4L C) 33.6L D) 40.0l
B) 22.4L This question can be solved using the ideal gas law PV = nRT or by knowing that the volume of one mole of gas at STP (1 atm and 0C) is 22.4L.
Given the half-reaction reduction potentials in the table below, which of the following reactions represents the overall equation for a lead-acid battery during its recharging cycle? Pb^2+ + 2e- --> Pb _________________________________________________E = -0.13 PbSO4 + 2e- --> Pb + SO4^2- _________________________________E = -0.36 PbO2 + 2e- + 4H+ + SO4^2- --> PbSO4 + 2H2O ___E = +1.69 PbO2 + 2e- + 2H+ --> Pb(OH)2 ________________________________E = +1.48 A) 2Pb(OH)2 --> PbO2 + Pb + 2H2O B) 2PBSO4 + 2H2O --> PbO2 + Pb + 2H2SO4 C) PbO2 + Pb + 2H2SO4 --> 2PbSO4 + 2H2O D) PbO2 + Pb + 2H2O --> 2 Pb(OH)2
B) 2PBSO4 + 2H2O --> PbO2 + Pb + 2H2SO4 The lead-acid battery operates under acidic conditions, not basic ones, so choices that contain Pb(OH)2 can be eliminated. During the recharging cycle, the battery is an electrolytic cell, not a voltaic cell, so the E should be negative.
Calculate the concentration of F- ions in a 2M solution of hydrogen fluoride, HF. (The Ka of HF is 6.8 x 10^(-4)). A) 1.4 x 10^(-3) M B) 3.7 x 10^(-2) M C) 1.2 x 10^(-2) M D) 1.8 x 10^(-2) M
B) 3.7 x 10^(-2) M
Which of the following best approximates the pH of a solution when 99.9% of the acid in a pH 1 solution is neutralized? A) 6.7 B) 4 C) 1 D) 7
B) 4
Which one of the following best approximates the pH of a solution when 99.9% of the acid in a pH 1 solution is neutralized? A) 6.7 B) 4 C) 1 D) 7
B) 4 The neutralization of 99.9% of acid tells us that for every one thousand H+ originally in solution, only one remains. A change in [H+] by a factor of 10^3 corresponds to a change of 3 pH units. If the initial pH was 1.0, then the final pH must be 4.
A chemist is working with a well-characterized reaction in her laboratory. Addition of an unknown compound to the reaction results in an increase in initial reaction rate. However, upon addition of larger quantities of the same compound, no further increase is detected. What is the most likely identity of the unknown compound? A) An intermediate. B) A catalyst. C) An inhibitor. D) A product.
B) A catalyst. Addition of a catalyst will increase the rate of a reaction by decreasing the activation energy of the step in question, but will not continue to do so with increasing concentrations of catalyst. While addition of an intermediate may increase the rate of a reaction, the initial rate will not plateau at higher concentrations (A is wrong). An inhibitor and product will decrease the reaction rate (C and D are wrong).
Which of the following substances, when added to a saturated solution containing both aqueous and solid silver chloride, will cause dissolution of the silver chloride solid through complex ion formation with Ag? A) Aqueous silver nitrate. B) Aqueous potassium cyanide. C) Aqueous sodium chloride. D) Aqueous sodium acetate.
B) Aqueous potassium cyanide. In order to solubilize the solid silver chloride, the aqueous ions must be consumed, causing the equilibrium to shift and dissolve more solid silver chloride. Alternatively, the silver chloride must be converted to a soluble substance, such as a complex ion. Aqueous potassium cyanide will cause the formation of the complex ion dicyanoargenate, resulting in the consumption of the solid silver chloride. Adding neutral salts of silver or chloride is the common ion effect and will reduce the solubility of silver chloride, causing more precipitation (A and C are wrong). The addition of sodium acetate will have no effect since both sodium and acetate salts are known to be completely dissociated in solution (D is wrong).
Each of the following are true of redox titrations EXCEPT: A) At the half-equivalence point, the concentrations of the oxidized nd reduced form of the analyte are equal. B) At the equivalence point, the number of moles of titrant added equals the number of moles of analyte at the start of the titration. C) At the equivalence point, the reaction between the analyte and titrant is complete. D) The reaction occurring during the titration involves the transfer of electrons between the titrant and analyte.
B) At the equivalence point, the number of moles of titrant added equals the number of moles of analyte at the start of the titration. By definition, at the half-equivalence point one-half of the original number of moles of analyte has reacted. This means the oxidized and reduced forms will both have the equivalent of half the original number of moles than at the start. Concentrations will also be equal. B is only true if for each half-reaction, the same number of electrons is lost in the oxidation half-reaction as is gained in the reduction half-reaction.
In organic solution, F- deprotonates dissolved HCl. Which of the following explains this observation? A) F- has a greater electronegativity than Cl-. B) F- has a smaller radius than Cl-. C) F- has a lower ionization energy than Cl-. D) F- is a stronger acid than Cl-.
B) F- has a smaller radius than Cl-. Since F- has a smaller radius than Cl-, it is less stable with excess charge, and therefore a better Bronsted base. Consequently, it outcompetes Cl- for the proton.
Which compound is a weak electrolyte? A) CaCl2 B) H2CO3 C) PbSO4 D) CH3OH
B) H2CO3 All ionic compounds are strong electrolytes, regardless of how soluble they are (A and C are wrong). Both carbonic acid and methanol are molecular compounds, but since carbonic acid dissociates to a small extent in solution (it's a weak acid) while methanol doesn't, B is the best answer. ....The Princeton explanation seems to support D even though they say the answer is B...
The following equilibrium exists in a closed container: N2(g) + O2(g) --> 2NO(g) deltaH = +181 kJ/mol Which of the following perturbations would favor the formation of NO(g)? A) Decreasing temperature. B) Increasing temperature. C) Decreasing pressure. D) Increasing pressure.
B) Increasing temperature. A positive delta H means the forward reaction is endothermic, so heat can be treated like a reactant. Thus increasing temperature will increase the forward reaction.
The standard delta G of a reaction increases following an increase in temperature. What impact would this have on the equilibrium constant? A) It increases. B) It decreases. C) It does not change. D) Inadequate information is provided to determine the outcome.
B) It decreases. As the standard delta G increases the reaction becomes less spontaneous and favors reactants to a greater degree. With an increase in reactants at equilibrium, the Keq decreases since K is a ratio of products/reactants. delta G naught = -RT ln(Keq), thus as delta G naught increases, K must decrease.
What is the expression for the acid dissociation constant (Ka) of sulfurous acid? A) Ka = ([H+]^2[SO3^2-])/[H2SO3] B) Ka = ([H+][HSO3^-])/[H2SO3] C) Ka = ([H+]^2[SO3^2-])/[HSO3^-] D) Ka = ([H+]^2[SO3^2-])/[HSO3^-]
B) Ka = ([H+][HSO3^-])/[H2SO3]
If the first measurements of the ideal gas constant were performed at high altitude instead of at sea level, what would be true of the derived value? A) Magnitude would be greater than 0.08 B) Magnitude would be 0.08. C) Magnitude would be less than 0.008. D) Magnitude could not be determined above sea level.
B) Magnitude would be 0.08. The constant works at all pressures and temperatures.
In an electrolytic cell containing molten MgCl2(l): A) Mg^2+ is reduced at the anode, and Cl- is oxidized at the cathode. B) Mg^2+ is reduced at the cathode, and Cl- is oxidized at the anode. C) Mg^2+ is oxidized at the anode, and Cl- is reduced at the cathode. D) Mg2+ is oxidized at the cathode, and Cl- is reduced at the anode.
B) Mg^2+ is reduced at the cathode, and Cl- is oxidized at the anode. Oxidation is always at the anode; reduction is always at the cathode.
In a fully charged led-acid battery, metallic Pb is one of the two electrode materials. Which of the following redox reactions is possible during recharge of a spent lead-acid battery? A) Pb --> PbSO4 + 2e- B) PbSO4 + 2e- --> Pb C) Pb --> PbO2 + 4e- D) Pb(H2O)4 + 2e- --> Pb
B) PbSO4 + 2e- --> Pb If Pb^0 is an electrode material in the fully charged battery, then it will be oxidized during discharge since anionic Pb is not feasible. The recharge reaction must then be the reduction of a cationic Pb species to Pb^0.
The following table shows the values of the van der Waals constants for a select group of gases: Gas_______a__________b______ He____0.0341___0.02370 O2_____1.360____0.03803 N2_____1.390____0.03913 CO____1.485____0.03985 CO2__3.592____0.04267 Based on these data, which of the following statements is true? A) The dipole-dipole forces between CO molecules is stronger than the London dispersion forces between CO2 molecules. B) The molecular size of oxygen is smaller than the molecular size of nitrogen. C) Oxygen should have a higher boiling point than carbon monoxide. D) Helium has the largest deviation to ideal behavior at high pressures.
B) The molecular size of oxygen is smaller than the molecular size of nitrogen. The strength of the intermolecular forces for real gases is directly proportional to the value of "a" in the van der Waals equation. The molecular size for real gases is directly proportional to the value of "b". Thus, because the "b" value is larger for N2 than O2, B is correct.
The following reaction is allowed to reach equilibrium: Cl2O(g) + 2OH- --> 2OCl-(aq) + H2O(l) What will be the effect of then doubling the hydroxide concentration? A) The reaction quotient will be 1/2 the equilibrium constant, favoring the forward reaction. B) The reaction quotient will be 1/4 the equilibrium constant, favoring the forward reaction. C) The reaction quotient will be twice the equilibrium constant, favoring the forward reaction. D) The reaction quotient will be four times the equilibrium constant, favoring the reverse reaction.
B) The reaction quotient will be 1/4 the equilibrium constant, favoring the forward reaction. When determining the reaction quotient, the reactants are in the denominator, so doubling a reactant will make the reaction quotient a fraction of the Keq. Because there are 2 moles of OH in the reaction, OH is to the second power in the denominator. Thus doubling [OH] from equilibrium concentrations will make the reaction quotient 1/4 of the Keq.
In the earth's crust, iron is predominantly found as iron ore (a mixture of iron oxides) while gold is found in its neutral, metallic form. Which of the following statements is most likely true? A) The reduction potential of metallic gold is larger than that of cationic iron. B) The reduction potential of cationic gold is larger than that of cationic iron. C) Gold is more easily oxidized than iron in the primarily aerobic environment of Earth. D) Iron oxides are composed of neutral iron bound to oxygen.
B) The reduction potential of cationic gold is larger than that of cationic iron.
Which of the following cells generates the greatest amount of energy per Coulomb? Zn^2+ + 2e- --> Zn _____E = -0.76 Al^3+ + 3e- --> Al ______E = -1.66 Ag+ + e- --> Ag _________E = +0.80 Cu+ + e- --> Cu _________ E = +0.52 A) Al | Al^3+ || Zn^2+ | Zn B) Zn | Zn^2+ || Cu+ | Cu C) Cu | Cu+ || Ag+ | Ag D) Ag| Ag+ || Cu+ | Cu
B) Zn | Zn^2+ || Cu+ | Cu Anode | Anodic solution [ ] || Cathodic solution [ ] | Cathode. Thus E = 0.76 + 0.52 = 1.28V, which is the option with the greatest value of E.
To increase the solubility of a gas in solution, you could: A) stir the mixture. B) cool the mixture. C) move the solution to a higher elevation. D) place it in a container under a vacuum.
B) cool the mixture. The solubility of a gas increases as temperature decreases. Stirring a solution has no impact on how much solute can dissolve in a solvent, although it can affect the rate at which a solute dissolves (A is wrong). The solubility of gasses increases as pressure increases and at higher elevation atmospheric pressure is lowered, therefore C and D are wrong.
As you move from left to right across the periodic table, the atomic radii of elements in the same period: A) decrease because the amount of shielding increases. B) decrease because effective nuclear charge increases. C) Increase because the amount of shielding decreases. D) Increase because of increased electron-electron repulsion.
B) decrease because effective nuclear charge increases. Moving left to right, more protons mean increased effective nuclear charges after the shielding of the inner core electrons are factored in. This increase means that electron-electron repulsion is more than counteracted by the increased effective nuclear charge, making B a better answer than D.
A spontaneous reaction can be made non-spontaneous if: A) delta H< 0, delta S > 0, and the temperature is raised. B) delta H < 0, delta S < 0, and the temperature is raised. C) delta H > 0, delta S < 0, and the temperature is lowered. D) delta H < 0, delta S > 0, and the temperature is lowered.
B) delta H < 0, delta S < 0, and the temperature is raised. For a reaction to change from spontaneous to non-spontaneous with a change of temperature, the binding energy would have to have been negative with a negative entropy. This would create a spontaneous reaction at low temperatures and a non-spontaneous reaction at high temperatures.
Two blocks of metal have the same mass, but the specific heat of Block 1 is greater than Block 2. If block 1 is cooler than block 2, which will be true if they are put in contact and allowed to come to thermal equilibrium? A) deltaT1 < 0 < deltaT2 and |delta T1| < |delta T2| B) deltaT2 < 0 < deltaT1 and |delta T1| < |delta T2| C) deltaT2 < 0 < deltaT1 and |delta T2| < |delta T1| D) deltaT1 < 0 < deltaT2 and |delta T2| < |delta T1|
B) deltaT2 < 0 < deltaT1 and |delta T1| < |delta T2| Because T1 < T2, heat will flow from block 2 to block 1, so the temperature change of block 1 will be positive and block 2 will be negative. Since Block 1 has a greater specific heat, its magnitude of change will be smaller.
A sample of solid Mg(OH)2 is added to water and reaches equilibrium with its dissociation ions. Addition of the strong base NaOH would most notably increase the concentration of: A) H3O+ B) undissociated magnesium hydroxide. C) undissociated sodium hydroxide. D) Mg2+
B) undissociated magnesium hydroxide.
What is the molecular geometry with 3 electron groups and 1 lone pair?
Bent.
What is the molecular geometry with 4 electron groups and 2 lone pairs?
Bent.
What is the most common type of beta decay?
Beta - Decay.
Ethylenediaminetetraacetic acid (EDTA) is a commonly used scavenger of heavy metals. The molecule has 4 carboxylic acid moieties, with successive pKa values of 1.99, 2.67, 6.16, and 10.26. At neutral pH, what is the predominant charge state of EDTA? A) -1 B) -2 C) -3 D) -4
C) -3 The deprotonated form of a compound is favored when pH > pKa. At neutral pH, this is true for 3 of the 4 acidic protons, giving a charge of -3.
What is the mole fraction of NaOH in a solution made from 80g NaOH (mw= 40) in 180g H2O (mw = 18)? A) 0.31 B) 0.20 C) 0.17 D) 0.11
C) 0.17 80g NaOH = 2 moles 180g H2O = 10 moles mole fraction = (n NaOH)/(n NaOH + n H2O) mole fraction = 2/(2+10) = 1/6 = 0.166
A high pressure gaseous synthesis of hydrazine (H4N2) at moderate temperatures is governed by the following equilibrium: 2NH3 --> H4N2 + H2, Keq = 10^-2 If 2 mol of each of the three species is added to the flask and the progression of the reaction is monitored, which of the following will be observed? A) A decrease in the concentration of NH3, and an increase in the concentrations of H4N2 and H2 B) An increase in the concentration of NH3, and an increase In the concentrations of H4N2 and H2 C) An increase in the concentration of NH3, and a decrease in the concentrations of H4N2 and H2 D) An increase in the concentration of H4N2, and a decrease in the concentrations NH3 and H2
C) An increase in the concentration of NH3, and a decrease in the concentrations of H4N2 and H2 The reaction quotient is 1, which is greater than the Keq of 10 ^-2, so it will proceed towards the reactants.
A drained battery is placed onto its charger causing its normal oxidation-reduction reaction to proceed in reverse. Which of the following best describes the changes in the cell? A) The cathode becomes the site of oxidation. B) The reverse reaction occurs spontaneously. C) Both electrodes maintain the same charge following reversal of reaction. D) Electron flow occurs from the cathode to the anode.
C) Both electrodes maintain the same charge following reversal of reaction. When a discharged batter is attached to a voltage source, the reaction proceeds in reverse. This results in the reversal fo the anode and cathode and the flow of electrons from the new anode to the new cathode. This reversal of the normally spontaneous reaction of a battery requires an attached voltage source, so it is nonspontaneous. In electrolytic cells, the cathode has a negative charge while the anode has a positive charge. Given that the electrodes changed from anode to cathode, the electrodes maintain the same charge following reversal fo the cell.
Based on the following half-reaction potentials, which is the strongest reducing agent? Sn^4+ + 2e- --> Sn^2+ ______E = -0.14 Ag+ + e- --> Ag_______________E = +0.80 Cr^3+ + 3e- --> Cr __________E = -0.74 Fe^2+ + 2e- --> Fe___________E = -0.44 A) Ag B) Fe^2+ C) Cr D) Sn^2+
C) Cr A reducing agent is the reactant that gets oxidized. therefore the species that is the best reducing agent is the one that is the most easily oxidized. Flipping each of the half-reactions accompanying this question reveals that the oxidation of Cr has a potential of +0.74, which is the greatest possible value.
A sample of nitrogen gas is cooled from 80C to 20C in a rigid-walled container. What impact would this have on pressure? A) increase to 1.2 times the original pressure. B) Increase by a factor of 4. C) Decrease to 0.8 times the original pressure. D) Decrease by a factor of 4.
C) Decrease to 0.8 times the original pressure. According to Amonton's Law P/T = P/T, but it must be in Kelvin. 293K/353K = ~0.8
Why is temperature constant during any phase change? A) All phases have the same energy, so no temperature change is observed during the phase transitions. B) Energy is used to break or form bonds rather than change temperature during a phase change. C) Energy is used to break or form intermolecular forces rather than change temperature during a phase change. D) Added or removed energy either decreases or increases the entropy
C) Energy is used to break or form intermolecular forces rather than change temperature during a phase change. The energy added to a system causing a phase change is used to break the intermolecular forces holding molecules together rather than make molecules move faster. Solids liquids and gases all have different potential energies, with solids having the lest and gases the most (A is wrong). A phase change is a physical, not chemical process, so no chemical bonds are broken or formed in the process (B is wrong). While a phase change does affect the entropy of the system, adding energy makes a more disordered system, thereby increasing entropy (D is wrong).
A titration of which of the following aqueous hydrogen halides with NaOH will show and equivalence point about pH = 7? A) HCl B) HI C) HF D) HBr
C) HF HF is the only weak acid of the hydrogen halide series, thus, when titrated with a strong base, it has a basic equivalence point. All other choices have equivalence points at or very near pH = 7.
Which one of the following can behave as a Bronsted-Lowrey acid, but not a Lewis acid? A) CF4. B) NaAlCl4. C) HF. D) Br2.
C) HF. A Bronsted-Lowry acid donates an H+, while a Lewis acid accepts a pair of electrons. Since a Bronsted-Lowrey acid must have an H in the first place, only choice C can be the answer.
Catalysts increase reaction rate by stabilizing the transition state. What impact does this have on the reverse reaction? A) No impact: a separate catalyst would be required for the reverse reaction. B) No impact: the reverse reaction is catalytically resistant. C) Increases reverse reaction rate to the same degree as the forward reaction. D) Increases reverse reaction rate by changing the reverse reaction intermediates.
C) Increases reverse reaction rate to the same degree as the forward reaction. Stabilizing the transition state increases the rate of the forward and reverse reactions to the same degree. Catalysts have no impact on equilibrium. Kinetics and thermodynamics are separate entities in chemistry.
A researcher investigates an endothermic reaction found to be non-spontaneous in a temperature-independent manner. Which of the following is the reaction being studied? A) 2 H2O(g) --> 2 H2(g) + O2(g) B) CO2(s) --> CO2(l) C) N2(g) + 2 O2(g) --> 2 NO2(g) D) N2O4(g) --> 2 NO2(g)
C) N2(g) + 2 O2(g) --> 2 NO2(g)
Which of the following pairs will have the strongest intermolecular forces between them? A) O2 and N2. B) HCl and CHCl3. C) NaCl and NH3. D) H2O and C8H18.
C) NaCl and NH3. The strongest intermolecular forces occur between molecules with a greater magnitude of charge. Na and Cl have full charges. Polar compounds will have large partial charges due to differences in electronegativity. Therefore, the ions in NaCl and the polar NH3 will form the strongest ion-dipole interactions.
A scientist adds reactants and an enzyme to a beaker placed on the benchtop. As the reaction proceeds, which of the following events would have the smallest effect on the rate of the forward reaction? A) More reactants are added to the beaker. B) The solution is stirred. C) Products are removed from the beaker. D) The temperature of the beaker is changed.
C) Products are removed from the beaker. While removing products will shift the equation to the right by Le Chatelier's Principle, this is an effect on the equilibrium, or thermodynamics, of the reaction and does not affect the rate of the forward reaction.
CO(g) + NO3(g) --> NO2 (g) + CO2(g) The overall reaction order for the elementary step above is: A) Zeroth Order. B) First Order. C) Second Order. D) Third Order.
C) Second Order. The rate law for this elementary step is rate = k [CO][NO3] which, due to each reactant being first order, is a second order process overall.
Which of the following will release the most energy with the addition of an electron? A) Al B) Ga C) Si D) Ge
C) Si. The energy released when an atom gains an electron in its valence shell is its electron affinity, which becomes more negative from bottom left to top right. As the radius decreases, an electron added to an atom has farther to fall to reach the valence shell closer to the nucleus, thereby giving off more energy. Since silicon is the smallest option, it has the most negative electron affinity, indicating the greatest gain in stability.
Where would the dissolved gas concentration be highest in a shallow body of water? A) Top B) Middle C) Bottom D) Constant
C) The bottom. Solubility of gas in liquid increases with increased pressure. Pressure will be the greatest at the bottom, so that is where the most gaseous solute will be found.
Which of the following statements concerning 50ml of basic solution composed of 02 M NaH2PO4 and 0.2 M Na2HPO4 is correct? A) With the addition of ammonia, a precipitate should be formed. B) The concentration of Na+ is 0.4M. C) The pH of the solution will not change with the addition of 20ml of water. D) The addition of 1ml of 0.1 M HCl to the reaction will result in a pH of 2.
C) The pH of the solution will not change with the addition of 20ml of water. This solution is a buffer. The pH of a buffer does not change with the addition or removal of water.
In the construction of a "lemon battery," a galvanized nail coated in zinc and a penny are inserted on opposite ends of a lemon. Each metal is then attached to a voltmeter by a wire and a reading of -0.85 V is obtained. Which of the following best describes the reading? A) The reaction is spontaneous, but requires a salt bridge to complete the circuit. B) The reaction is nonspontaneous and requires a power source to proceed. C) The reaction is spontaneous but the leads from the voltmeter to the anode and cathode have been reversed. D) The reaction is nonspontaneous and will proceed without a power source.
C) The reaction is spontaneous but the leads from the voltmeter to the anode and cathode have been reversed. The voltage reading can be thought of as the E cell value. Thus, to be spontaneous it should be positive, not negative. If the reading is negative but the reaction is positive, then the leads must have been reversed.
The van der Waals equation for real gases contains two constants which have unique values for each gas. When comparing these constants for neon and argon, the constant "a" is larger for argon because: A) argon has larger particles than neon. B) argon has more protons than neon. C) argon has stronger intermolecular forces than neon. D) argon has greater density than neon.
C) argon has stronger intermolecular forces than neon. The constant "a" is a correction for the attractive forces between the gas molecules. The larger the value of "a," the stronger the intermolecular forces of the gas in question.
Addition of sodium acetate to a solution of acetic acid will cause the pH to: A) remain constant because sodium acetate is a buffer. B) remain constant because sodium acetate is neither acidic nor basic. C) increase due to the common ion effect. D) decrease due to the common ion effect.
C) increase due to the common ion effect. Sodium acetate is a basic compound because acetate is the conjugate base of acetic acid, a weak acid. The addition of a base to any solution, whether it is buffered or not, will increase the pH.
Water boils at a lower temperature at high altitudes. The most likely explanation for this is that at high altitudes: A) the vapor pressure of water is increased. B) more energy is available to break bonds in liquid molecules. C) the atmospheric pressure is lower than at low altitudes. D) the temperature is higher than at low altitudes.
C) the atmospheric pressure is lower than at low altitudes.
Does plating occur on the cathode or anode?
Cathode
In electroplating, is the object to be covered on the anode or cathode side?
Cathode.
What elements achieve a lower energy state by having a filled or half-filled d subshell?
Chromium, molybdenum. Copper, silver, and gold.
How can Ka and Kb be used to determine the direction of the reaction?
Compare Ka with Kb. The larger value will determine the reactant in the favored direction of the reaction.
The formation constant (Kf) for the complex ion [Fe(en)3]^2+ is 5.0 x 10^9, whereas the Kf for [Fe(ox)3]^4- is 1.7 x 10^5 (en = 1,2diaminoethane, ox = oxalate anion). Based on this information, which of the following statements is true? A) The higher the oxidation state on the transition metal, the larger the formation constant. B) Complexes with bidentate ligands always have higher Kf values than the corresponding monodentate complexes. C) A reaction between oxalate ion and [Fe(en)3]^2+ will form [Fe(ox)3]^4- completely. D) 1,2-Diaminoethane is a stronger ligand with iron(II) than the oxalate ion.
D) 1,2-Diaminoethane is a stronger ligand with iron(II) than the oxalate ion.
A mixture of acidic wastes is found to be 2 M H2SO4, 0.5 M HI, and 3M HNO3. What volume of 5M NaOH solution will be required, per liter of acidic waste, to completely neutralize the acid? A) 1.5 ml B) 1.1 L C) 3.0 L D) 1.5 L
D) 1.5 L. (H2SO4 is diprotic.)
The radioactive isotope 32P has a half-life of 14 days. If 200mg of 32P remains in a vial, approximately how much existed 60 days prior? A) 0.8 g B) 1.6 g C) 3.2 g D) 3.9 g
D) 3.9 g Since the question is asking for a past mass, the mass must double at each half-life. The period of 60 days is between four and five half lives and thus represents a minimum of four doublings. Doubling the mass four times gives 200mg, 400mg, 800mg, 1600mg, 3200mg, or 3.2g. D is the only option with a value greater than 3.2g and is thus the answer.
Chlorosulfonic acid (HSO3Cl, MW = 116) is stronger than sulfuric acid when solvated in water, yet it is far less acidic in common organic solvents. When 1.16g of HSO3 is dissolved in 10ml of hexane, spectroscopic methods determine the [SO3Cl-] to be 2.2 x 10^(-3) M. Which of the following is closest to the pKa fo chlorosulfonic acid in hexane? A) 6.2 B) 2.8 C) 0.2 D) 5.4
D) 5.4
Al^3+ + 3e- --> Al_______________E = -1.67 Au^3+ + 3e- --> Au ____________E = +1.50 Based on the half-reactions listed above, which of the following has the strongest activity? A) Au^3+ as a reducing agent. B) Au as a reducing agent. C) Al^3+ as an oxidizing agent. D) Al as a reducing agent.
D) Al as a reducing agent. The greatest positive E value will correlate with the most spontaneous reaction (greatest activity). The aluminum reaction's E value has a greater magnitude than gold's. Because it is negative, the reaction must be reversed to be spontaneous.
A reaction between two species is experimentally observed to be second order overall. If the concentration of one of the species doubles, what happens to the reaction rate? A) The rate is halved. B) The rate quadruples. C) The rate doubles. D) Cannot be determined.
D) Cannot be determined. There are three ways for a two species reaction to produce an overall second order rate law: 1. rate = k[A][B] 2. rate = k[A]^2 3. rate = k[B]^2 Thus doubling A could double the reaction (1), quadruple the reaction (2), or have no effect (3). More information would be needed to answer properly.
Which of the following statements about stable chemical isotopes is FALSE? A) Many stable isotopes are naturally occurring. B) Isotopes can be separated by both chemical and physical means. C) Theoretical rate constants of decay are very small. D) Changing the number of neutrons has little effect on nuclear reactivity.
D) Changing the number of neutrons has little effect on nuclear reactivity. Changing the number of neutrons directly affect nuclear stability, particularly for lighter elements. The remaining choices are true statements. Isotopes can be separated by physical (centrifugation) and chemical means (variable reaction rate).
In the galvanic cell Ni | Ni^2+ || Fe^3=, Fe^2+ | Pt, what best describes the direction of current flow and flow of Na+ from the salt bridge? A) Current flows from Ni to Pt, and Na+ flows toward Ni. B) Current flows from Ni to Pt, and Na+ flows toward Pt. C) Current flows from Pt to Ni, and Na+ flows toward Ni. D) Current flows from Pt to Ni, and Na+ flows toward Pt.
D) Current flows from Pt to Ni, and Na+ flows toward Pt. In electrochemical cells, electrons flow from anode to cathode, thus current by definition flows from cathode to anode. In this cell, Ni^2+ is being oxidized and nickel is the anode, while Fe3+ is being reduced at a platinum cathode. Thus current flows from the Pt cathode to the Ni anode. Na+ travels form the salt bridge to the cathode to offset the charge imbalance generated by the current (Cations migrate to the Cathode).
Which of the following would have the biggest decrease in entropy for a gas in a piston cylinder? A) Compression. B) Doing work on the gas. C) Cooling. D) Deposition.
D) Deposition.
A voltaic cell is run for one hour at 2A and 1.4 grams of solid iron are formed. Assuming a one-to-one mole ratio of solid iron to its oxidized form, iron in which oxidation state served as the reactant? A) Fe+ B) Fe^0 C) Fe^2+ D) Fe^3+
D) Fe^3+
A sample of water is in equilibrium between the solid, liquid, and gaseous phases. Which of the following perturbations will result in generating only liquid water? A) Decreasing temperature. B) Increasing temperature. C) Decreasing pressure. D) Increasing pressure.
D) Increasing pressure.
Solubility Salt_________0 deg C______100 deg C KNO3_______13.3_____________247______ NaCl________35.7_____________39.8_____ A chemist attempts to purify a mixture of NaCl and KNO3 by recrystallization. Based on the information in the table above, which salt would she most likely recover as the precipitate in this process? A) NaCl, because it has a higher solubility at low temperatures. B) NaCl, because it has a lower solubility at higher temperatures. C) KNO3, because it has a higher solubility at high temperatures. D) KNO3, because it has a lower solubility at low temperatures.
D) KNO3, because it has a lower solubility at low temperatures. A solid needs to be soluble at high temperatures and insoluble at low temperatures in order to recover it as a precipitate via recrystallization.
SO2(g) + 1/2 O2(g) --> SO3(g) What is the equilibrium expression for the reaction above? A) Keq = [SO2][O2]^(1/2) / [SO3] B) Keq = [SO3]^(2) / [SO2]^(2) [O2] C) Keq = [SO3] / [SO2][O2] D) Keq = [SO3]/[SO2][O2]^(1/2)
D) Keq = [SO3]/[SO2][O2]^(1/2) B would have been more appropriate if the reaction had been balanced with whole number coefficients.
The acidic strength of HF is greatly enhanced when it is used in conjunction with SbF5. The resultant system, known as "magic acid," is one of the strongest acids known, and follows the dissociation equation below. HF + SbF5 --> H+ + SbF6- Which of the following best describes the role of SbF5 in magic acid? A) Bronsted base. B) Bronsted acid. C) Lewis base. D) Lewis acid.
D) Lewis acid. SbF5 accepts an electron pair on F- from dissociating HF, thus driving this dissociation reaction toward nearly full dissociation. SbF5 neither accepts nor donates H+, thus it acts as neither a Bronsted acid nor base.
An intern in a laboratory is asked to clean up after a new graduate student in the lab who was making a HEPES buffered solution. The intern finds a white solid powder left on the counter from the buffer preparation and is uncertain how to dispose of it. Which of the following is most likely identity of this white powder. A) Na. B) H2SO4. C) C3H6O. D) NaC3H5O3
D) NaC3H5O3 The intern was disposing of a white powder, thus we are looking for the compound that will have the strongest intermolecular forces and is consequently most likely to be solid. Ionic interactions are stronger than any other intermolecular forces (including H2SO4's H-bonding and C3H6O's dipole-dipole interactions), so it is the answer.
Resonance structures are two or more structures where: A) only atoms may move around. B) only bonding electrons may move around. C) only nonbonding electrons may move around. D) only nonbonding electrons, and double and triple bonds may move around.
D) Only nonbonding electrons and double and triple bonds may move around.
A sample of helium gas at 300C and 600 torr is in a 200L container. If the temperature of the gas is raised to 900C at constant volume, how is the pressure of the gas affected? A) Pressure will increase by a factor of 3 since pressure and temperature are directly related. B) Pressure will be unaffected in this instance due to the large volume of the container. C) Pressure will decrease by a factor of 3 since pressure and temperature are inversely related. D) Pressure will increase by a factor of 2 since the temperature increases by 600C.
D) Pressure will increase by a factor of 2 since the temperature increases by 600C. When predicting changes for gases, temperature must be in Kelvin. After converting these temperatures to 573 K and 1173 K, it is apparent that this is roughly a doubling of the absolute temperature. Because P/T = P/T, this means the pressure will also roughly double.
The equilibrium between methylamine bound, and unbound, to iron pentacarbonyl is found to have a constant Keq of ~30 and an activation energy of 13 kcal/mol. NH2CH3 + Fe(CO)5 --> (CH3NH2)Fe(CO)5 If the amine is switched to the very bulky diisopropylethylamine, the activation energy of binding is found to increase to 39 kcal/mol. With this data, approximately what is the new value of Keq? A) Keq will increase by a factor of 3. B) Keq will decrease by a factor of log 3. C) Keq will decrease by a factor of 3. D) There is no information in the question to determine the new Keq.
D) There is no information in the question to determine the new Keq. Activation energies are strictly kinetic measurements; they say nothing about the thermodynamics of a system.
Which of the following elements would be expected to exhibit the greatest ionization energy? A) Scandium (G3 P4). B) Potasssium (G1 P4). C) Calcium (G2 P4). D) Titanium (G4 P4).
D) Titanium (G4 P4). Ionization energy generally increases as we move to the right across a period, therefore titanium should have the highest ionization energy.
Which of the following statements about solids is true? A) The intramolecular bonds of a molecular solid are the same as its intermolecular forces. B) Ionic solids have a lower melting point than molecular solids. C) Network solids have greater electrical conductivity than metallic solids. D) Unlike network solids, metallic solids are ductile.
D) Unlike network solids, metallic solids are ductile. Metallic solids are unique in their covalently-bound lattice of nuclei surrounded by a sea of valence electrons. This makes them excellent conductors, malleable, and ductile. The intramolecular bonds of an ionic solid and of a networks solid are the same as their respective intermolecular forces, but molecular solids have covalent intramolecular forces and van der Waals intermolecular forces.
When an element is oxidized, it will: A) gain electrons, and its oxidation state will increase. B) gain electrons, and its oxidation state will decrease. C) lose electrons, and its oxidation state will decrease. D) lose electrons, and its oxidation state will increase.
D) lose electrons, and its oxidation state will increase.
2 NO + O2 --> 2 NO2 Which of the following characterizes the rate for the reaction above? A) rate = -delta [NO]/delta t B) rate = -2 delta [O]/ delta t C) rate = - delta [NO2]/ delta t D) rate = - (1/2) delta [NO]/ delta t
D) rate = - (1/2) delta [NO]/ delta t Reaction rate can be characterized by changes in reactants or products over time. The change in concentration of any product or reactant is multiplied by the reciprocal of its coefficient and divided by change in time. Reactants are negative and products are positive. Thus any of the following would have been correct: rate = -(1/2) delta [NO] / delta t rate = - delta [O2] / delta t rate = +(1/2) delta [NO2] / delta t
Equilibrium Constant
Does not include solids or solvents.
In what direction do electrons travel in a concentration cell?
Electrons go towards the higher concentration of positive ions.
In what direction do electrons travel in a galvanic cell?
Electrons travel from the anode to the cathode.
List the 9 most electronegative elements from strongest to weakest.
F, O, N = Cl, Br, I, S, C = H.
Rank the following species by increasing boiling point: I. CH3CHO. II. F2. III. CH3OH IV. KBr.
F2 < CH3CHO < CH3OH < KBr
What is the best possible formal charge for any given molecule?
Formal charges of all 0.
What is another word for melting?
Fusion.
What is the final phase of a 36g water vapor sample at 400C after removal of 15kJ of energy? delta H fus = 6.0 kg/mol delta H vap = 40.6 kg/mol c(solid) = 38.0 J/molK c(liquid) = 74.5 J/molK c(gas) = 36.0 j/molK
Gas q = 2n(36J/molK)(400-100) q = 21,600 > 15,000, therefore the energy is not sufficient to reduce the temperature of the water to 100C, so it will be in the gaseous phase.
Van't Hoff Factor. Ionizability Factor. (i)
How many ions one unit of a substance will produce in a solution.
What are the 3 possible oxidation states for hydrogen and when are they used?
Hydrogen is +1 when bound to elements more electronegative than carbon. Hydrogen is 0 when bound to carbon. Hydrogen is -1 when bound to elements less electronegative than carbon.
What equation is used to determine the number of moles that can be plated per second?
I = current n = moles F = 96,485 C/mol e- t = seconds
Which of the following are advantageous properties for a titrant to have in a redox titration? I. The net electrochemical reaction must have positive electric potential. II. The titrant must be able to be standardized or exist in a pure solid form. III. The titrant must have different colors for its reduced and oxidized forms.
I and II. The net electrochemical reaction must have positive electric potential and the titrant must be able to be standardized or exist in a pure solid form. I is true because delta G must be negative for the reaction to occur, so E must be positive. II is true because all titrants for all titrations need to have a known concentration with a high degree of certainty, thus a solution must be able to be made from a dry, pure sample for standardization. III is false. Although having a titrant that has two different colors for its oxidized and reduced forms within the titration is helpful, it is not required. All redox titrations have the advantage that by measuring the potential of the solution during the titration, one can determine the equivalence point of the titration by using graphical methods of analysis.
Which of the following species has/have a trigonal planar shape? I. PF3. II. CO3^2- III. BCl3
II and III only. PF3 has four electron groups around the central phosphorus, 3 bonds to fluorine and 1 lone pair. It is therefore trigonal pyramidal. BCl3 and CO3^-2 both are trigonal planar.
In a Galvanic cell, does the size of the cathode increase or decrease as it runs?
Increase.
How would intermolecular forces cause a deviation from ideal gas behavior?
Increased particle interactions would lead to fewer collisions with the walls of the container and a smaller transfer of momentum in collisions that do occur. The resulting pressure would be smaller than ideal.
How does atomic radius change along the periodic table? Why?
It decreases from left to right because the nucleus is increasingly positive, attracting electrons in their set orbitals. It increases from top to bottom due to increased nuclear shielding and additional orbitals.
How does the atomic radius of gallium (G13 P4) compare to the atomic radius of calcium (G2 P4)?
It is smaller because increased nuclear charge causes electrons to be held more tightly.
What is the limitation of Bohr's Model?
It only accurately describes behavior of atoms containing one electron.
Why is the salt bridge necessary in a galvanic cell?
It serves as a conduit for cations to travel to the cathode and anions towards the anode. This completes the circuit to allow current in the wire to continue.
What information does the reaction quotient give when compared to the equilibrium constant?
It tells which direction the reaction will proceed in order to reach equilibrium.
When a bond is formed, is enthalpy positive or negative?
It's negative (released).
When a bond is broken, is enthalpy positive or negative?
It's positive (requires energy input).
Would a sample that was quickly decaying have a large or small decay constant?
Large. The shorter the half-life, the larger the decay constant, the faster the decay.
What is the molecular geometry with two electron groups and no lone pairs?
Linear.
What reactants are used in determining the rate of a reaction?
Only the reactants involved in the rate-determining step.
What can be used instead of concentrations to determine the equilibrium for gaseous mixtures?
Partial pressures.
What is the SI unit for pressure?**************************************
Pascal (Pa) = N/m2
What is another name for Beta + decay?
Positron Emission.
What is the gas constant "R"?
R = 0.0821 Latm/Kmol
How are rate laws determined?
Rate laws can only be experimentally determined. 1. Use the general formula rate = k [A]^(x)[B]^(y). 2. Make sure all the powers of 10 are the same 3. Find two determinants to compare where only the species of interest's concentration changes. 4. If the concentration changes but the rates do not, it is 0 order. If the concentration and rate change by the same ratio, it is 1st order. If the change in concentration is 1:4 compared to the change in rate, it is 2nd order. 3. The constant k can be found by plugging in values from any determination.
Phase changes that bring molecules together ___________ heat.
Release.
Cell Diagram
Shorthand notation to identify the species present in a galvanic cell. If concentrations are not specified, assume 1M. Anode | Anodic solution [ ] || Cathodic solution [ ] | Cathode.
Le Chatelier's Principle
Systems resist deviation from the equilibrium. Adding reactants will cause more product to be produced. Adding products will cause more reactants to be produced. Heat can also be treated as a reactant or product.
For a given reaction, what can change the equilibrium constant?
Temperature. Changed pressures will cause shifts when there are different stoichiometric moles of gaseous products than reactants.
What is the molecular geometry with 4 electron groups and no lone pairs?
Tetrahedral.
What is the Ka value called?
The acid-ionization or acid-dissociation constant.
How does acidity change along the periodic table?
The acidity follows the electronegativity trend from left to right, but it increases from top to bottom because larger anions have more space to distribute negative charge, with greater distribution leading to greater stabilization.
A student performs Millikan's charged oil droplet experiment and is able to suspend an oil drop with no velocity. The mass of the oil drop is known, and the electric field strength required to suspend it is recorded. If F(grav) = mg and F(elec) = Qe are used to solve for the magnitude of charge on an electron, what is the most likely result?
The calculated charge will too high because buoyancy is not considered. Before the voltage source is turned on, the oil drop falls due to the gravitational force, F(grav). However, it also experiences an upward buoyant force (FB) which directly opposes Fgrav. Therefore the formulae to the left should have been used. Without considering FB, the forces would have been overestimated and thus the charge would be overestimated.
Reaction rates can be characterized by changes in reactants or products over time. How can reaction rates be expressed this way?
The change in concentration of any product or reactant is multiplied by the reciprocal of its coefficient and divided by change in time. Reactants are negative and products are positive.
Why are reduction potentials NEVER multiplied by the coefficients when balancing electrons?
The electric potential is the energy per unit charge, regardless of the number of times the reaction needs to run.
Which is greater: the first ionization energy or the second?
The first ionization energy.
A sealed container contains NO2, a brownish-red gas, and N2O4, a colorless gas, at equilibrium at 0C according to the following reaction: 2NO2(g) --> N2O4(g). How will the color of the gas mixture change if the container is placed in dry ice and acetone at -78C?
The gas mixture will become lighter in color. If the system is at equilibrium at 0C, delta G must be 0. during the forward reaction, 2 moles of gas are converted to 1 mole, decreasing entropy. Since entropy is negative, the sign of H can be determined. delta G = delta H - T(delta S) 0 = delta H - T(delta S) - deltaH = - T(delta S) Therefore, if S is negative then H must also be negative. A negative delta H value means the forward reaction is exothermic, so heat can be treated like a product. Thus if temperature is decreased to -78C, the reaction will shift towards to product side, creating more N2O4 and turning the gas a lighter color.
What is the relationship between the constant "a" in the van der Waals equation and intermolecular forces?
The greater the intermolecular forces, the greater the value of a.
How is nuclear binding energy related to stability?
The greater the nuclear binding energy per nucleon, the greater the stability.
What is the relationship between the degree of s character in the hybrid orbitals and bond length?
The greater the s character, the shorter the bond.
What is the relationship between the constant "b" in the van der Waals equation and the size of the molecule?
The greater the size of the molecule, the greater the value of b.
How does altitude affect water's boiling point?
The higher the altitude, the higher the boiling point due to the negative solid-liquid boundary line.
What is the relationship between bond order and bond length?
The higher the order, the shorter the length.
What is the relationship between vapor pressure and temperature?
The higher the temperature, the higher the vapor pressure.
What is the relationship between vapor pressure and evaporation?
The higher the vapor pressure, the more easily evaporation occurs.
Why do alkalai metals become increasingly reactive going down the group?
The ionization energy decreases from top to bottom.
What is the relationship between Ka and acid strength?
The larger the Ka value, the stronger the acid.
What is the relationship between Kb and base strength?
The larger the Kb value, the stronger the base.
What is the relationship between pKa and acid strength?
The lower the pKa, the stronger the acid.
The more negative the reduction potential, the _______________ the reactant is as an oxidizing agent, and the ________________ the product is as a reducing agent.
The more negative the reduction potential, the weaker the reactant is as an oxidizing agent, and the stronger the product is as a reducing agent.
Ion Product Qsp
The reaction quotient for a solubility reaction.
What is the relationship between bond length and bond strength?
The shorter the bond, the stronger the bond.
How is solubility affected by pressure?
The solubility of gases in liquids tends to increase with increasing pressure. The solubility of a gas in a liquid is a function of the partial pressure of that gas above the liquid and Henry's law constant (solubility = kP).
What determines orbital geometry?
The total number of electron groups for a given atom.
How would non-negligible volumes of gas particles cause a deviation from ideal gas behavior?
The volume of a gas is defined as the free space in which the particles can move. At high pressures, the volume occupied by each particle becomes a greater proportion of the gas sample, causing a decrease in volume.
What is the standard molar volume?
The volume of one mole of any ideal gas at 0 degrees Celsius and 1 atm is 22.4L.
What is the relationship between solubility and pressure?
They are directly proportional. The higher the pressure, the greater the solubility.
What is the relationship between temperature change and heat capacity?
They are inversely related. The higher the heat capacity, the smaller the temperature change.
Do halogens act as reducing or oxidizing agents?
They are oxidizing agents, readily accepting an additional electron to complete their octet.
Do alkali metals and alkaline earth metals act as reducing or oxidizing agents?
They are reducing agents, readily giving their valence electrons.
How do diamagnetic atoms respond to external magnetic fields?
They are repelled.
How do atomic numbers and mass numbers vary between isotopes?
They have the same atomic number, but different mass numbers.
Determine the hybridizations of Na-c in the molecule on the reverse side.
To find formal charge, count the number of electron groups around the atom. Lone pairs delocalized by resonance are an exception; they are sp2-hybridized even though they appear to be sp3. Thus N(a), (b), and (c) are all sp2-hybridized.
Which class of elements always lose s electrons before they lose d electrons?
Transition metals.
What is the molecular geometry with 4 electron groups and 1 lone pair?
Trigonal Pyramidal.
What is the molecular geometry with 3 electron groups and no lone pairs?
Trigonal planar.
How is pH calculated with strong acids?
Use the molarity of the solution to calculate the pH directly.
When does gamma decay occur?
When the nucleus is in an excited state after alpha or beta decay.
SEE OTHER SIDE OF THE FLASHCARD FIRST When the y-axis is pH, titrations of acids should have a positive trend while titrations have a negative trend (eliminate A and C). Strong acids/base titrated with strong bases/acids have equivalence points near 7, whereas weak bases titrated with strong acids will have acidic equivalence points and weak acids titrated with strong bases will have basic equivalence points.
Which graph best represents the titration of a weak base with HCl?
What are the X- and Y- axis on a phase diagram?
X-axis: Temperature. Y-axis: Pressure.
What are the X- and Y- axis on a phase transition diagram?
X-axis: heat added. Y-axis: temperature.
A researcher places a sample of radiolabeled AgI into a saturated solution of non-radiolabeled AgI and several hours later inadvertently spills some of the liquid on a nearby countertop. Is the researcher in danger while cleaning this spill?
Yes, a portion of the radioactive iodide in the solid would have been replaced by the non-radiolabeled isotope.
Does a small atomic radius correspond to a high ionization energy? Why or why not?
Yes, because the shorter distance between the positive nucleus and the negative electron enhances electrostatic attraction, and thus makes it difficult for these electrons to be removed.
If the pH > pKa, then the acid will be _____________________.
deprotonated
The ____________ the concentration of the reactants, the faster the reaction rate.
greater
The ____________ the temperature of the reaction mixture, the faster the reaction rate.
higher
The ____________ the activation energy, the faster the reaction rate.
lower
When q is ______________, heat is absorbed.
positive.
If the pH < pKa, then the acid will be ______________________.
protonated
What are the hybridization, orbital geometry, and bond angle of an atom with 2 electron groups?
sp 180degrees Linear
What are the hybridization, orbital geometry, and bond angle of an atom with 3 electron groups?
sp2 120 degrees Trigonal planar.
What is the hybridization of the central atom in PCl3?
sp3
What are the hybridization, orbital geometry, and bond angle of an atom with 4 electron groups?
sp3 109.5 degrees Tetrahedral.