mcat chem Kinetics and Equilibrium, Electrochemistry and Nuclear Chemistry, Acids and Bases

MnO4-(aq) + 8 H+(aq) + 5 Fe2+(aq) → 5 Fe3+(aq) + Mn2+(aq) + 4 H2O(l) It takes 35 mL of a 0.093 M solution of potassium permanganate to react completely with 10 mL of an aqueous solution of iron(II) in a redox titration, according to the reaction above. Which of the following represents the molarity of the iron(II) solution?

(5)(35)(0.093)/(10)

The reduction potentials of the reactions below are +1.2 V and -0.8 V, respectively. MnO2(s) + 4 H+ + 2e- → Mn2+(aq) + 2 H2O(l) Zn2+(aq) + 2e- → Zn(s) What is the voltage of a MnO2/Zn(s) cell?

+2.0 V

The oxidation states of sulfur in SO42- and SO32- are (respectively):

+6 and +4

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?

-3

The resulting solution made from the combination of 50 mL of 1.0 M LiOH with 50 mL of 1.0 M HBr will be identical in all respects to 100 mL of:

0.5 M LiBr. The best way to approach this question is to ignore OH- and H+, because they will neutralize each other when mixed. Thus, in this question we are mixing 50 mL of 1.0 M Li+ and 50 mL of 1.0 M Br-. Since the solution volume is doubling, the concentration of each ion is expected to decrease by a factor of 2. Therefore, the correct choice is "0.5 M LiBr

In the span of two hundred minutes, 30 grams of copper is plated on a sample of iron with a constant current of 3.8 A. How many moles of electrons are transferred per mole of plated copper? Note: F = 96,500 C/mol e-

1 Given I = C/t, we can rearrange to get C = I/t where I is current (in amps), C is a measure of charge (in coulombs), and t is time (in seconds).

Given that a parent and a daughter nucleus are isotopes of the same element, the ratio of alpha to beta decays which produced the daughter must be which of the following?

1 to 2

The formation constant (Kf) for the complex ion [Fe(en)3]2+ is 5.0 x 109, whereas the Kf for [Fe(ox)3]4- is 1.7 x 105 (en = 1,2 diaminoethane, ox = oxalate anion). Based on this information, which of the following statements is true?

1,2-Diaminoethane is a stronger ligand with iron(II) than the oxalate ion.

What is the pOH of a mixture made by adding 150 mL of 0.20 M sodium hydroxide to 50 mL of 0.20 M hydrochloric acid?

1.0 M x V = (0.20 M)(150 x 10-3 L) = 30 x 10-3 mol NaOH The moles of acid added are: M x V = (0.20 M)(50 x 10-3 L) = 10 x 10-3 mol HCl so pOH = -log(0.1) = 1.0

A mixture of acidic wastes is found to be 2 M H2SO4, 0.5 M HI, and 3 M HNO3. What volume of 5 M NaOH solution will be required, per liter of acidic waste, to completely neutralize the acid?

1.5

What percentage of HF (pKa = 3.17) dissociates in one liter of solution containing two moles of the acid?

1.8%

If a solution with a pH of 11 is diluted with pure water until the volume is increased by a factor of 10, the pH will then equal:

10

The Ka of formic acid (HCOOH) is 1.8 × 10-4. What is the pKb of the formate ion?

14 + log (1.8 × 10-4)

How many neutrons are in the daughter nuclide after 231Th undergoes beta emission?

140

Which of the following best describes the reduction half-reaction in the following reaction? Cu(s) + 2 NO3-(aq) + 4 H+(aq) → Cu2+(aq) + 2 NO2(g) + 2 H2O(l)

2 NO3-(aq) + 2 e- + 4 H+(aq) → 2 NO2(g) +2 H2O(l)

Twenty milliliters of a 8.4 x 10-3 M solution of HBr is added to sixty milliliters of water. What is the final pH of the solution?

2.7 Using C1V1 = C2V2, we find our final concentration to be 2.1 x 10-3 M.

In which of the following redox reactions are exactly six moles of electrons transferred?

3 Pd(s) + Na2Cr2O7 + 14 HNO3 → 3 Pd(NO3)2 + 2 Cr(NO3)3 + 7 H2O + 2 NaNO3

The Ka of a buffer is 4.5 × 10-4. If the concentration of undissociated weak acid is equal to the concentration of the conjugate base, the pH of this buffer system is between:

3 and 4.

Calculate the concentration of F- ions in a 2 M solution of hydrogen fluoride, HF. (The Ka of HF is 6.8 × 10-4.)

3.7 × 10-2 M

Because it dissolves carbon dioxide from the atmosphere to make mild carbonic acid, natural rain has a pH of around 5.5. However, due to pollutants such as sulfates from coal-fired power plants and nitrates from car exhausts, the pH of rain can drop to as low as 2. This decrease in pH represents a change in H+ concentration by approximately what factor?

3000

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?

4 The pH of a solution when 99.9% of the acid in a pH 1 solution is neutralized is 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 103 corresponds to a change of 3 pH units. If the initial pH was 1.0, then the final pH must be 4.

Phosphorus-32 has a half-life of 14 days. If a sample of 32P originally gave a reading of 100 milliCuries, what is the reading after 49 days?

8.8 mCi

thallium-201 decays by electron capture. What are the atomic and mass numbers of the daughter nucleus, respectively?

80, 201 Electron capture involves the addition of an electron to the nucleus with the conversion of a proton to a neutron

Addition of which of the following salts will most likely result in a precipitate when mixed with an aqueous solution of AgNO3?

Addition of NaCl will most likely result in a precipitate when mixed with an aqueous solution of AgNO3. 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.

Which of the following pairs will generate an electrolytic cell with the least stable products? Al3+ + 3 e− → Al(s) E° = -1.68 V Cd2+ + 2 e− → Cd(s) E° = -0.40 V Ag+ + e− → Ag(s) E° = 0.80 V Br2(l) + 2 e− → 2Br− E° = 1.08 V

Al3+ and Ag(s) The electrolytic cell with the most negative electrical potential will have the least stable products

N2(g) + 3 H2(g) 2 NH3(g), ΔH = -22 kcal/mol What is the effect of decreasing the volume of the system?

An increase in the forward reaction due to increased pressure

A chemist creates a concentration cell with equal volume half-cells (Cu|Cu+ (0.030 M)||Cu+ (1.0 M)|Cu), allows it to react for several minutes, and analyzes the solutions before the system has reached equilibrium. What best describes the concentrations seen in the cell at this time?

Anode = 0.100 M Cu+; cathode = 0.93 M Cu+

Which of the following best describes a corrosion pit?

Anode of a corrosion cell Corrosion pits and crevices are essentially spontaneous electrochemical cells. The metal is oxidized to an ionic form in the pit or crevice, and the electrons that are lost can react in a reduction reaction at a distant surface site of the metal. Since the pit or crevice is the site of oxidation, it must be an anode.

Which of the following can be deduced from the following reaction? 2 Fe2+ + H2O2 + 2 H+ → 2 Fe3+ + 2 H2O

At equilibrium, the products are favored. As this reaction has a positive potential, it is spontaneous and the products must therefore be more stable than the reactants and favored at equilibrium

Which of the following decay modes would be best in stabilizing a nucleus with too many neutrons?

Beta emission

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?

Both electrodes maintain the same charge following reversal of the reaction

Which of the following would exhibit a color change only at the end of the titration of 20 milliliters of 0.75 M NaOH into 60 milliliters of 0.25 M HClO4?

Bromothymol blue (pKa = 7.1)

Which of the following best characterizes electron flow in an electrolytic cell?

C. Electrons flow from anode to cathode due to the driving force provided by an external source. in galvanic cells, this flow of electrons occurs spontaneously as electrons flow down their potential gradient. For an electrolytic cell (which we are being asked about here), the intrinsic potential difference between the materials that constitute the anode and cathode is negative, indicating the given reaction is nonspontaneous and the flow of electrons from anode to cathode requires assistance from an external source, such as a battery

Which of the following compounds is a weak electrolyte?

CH3COOH

Which of the following is the conjugate species formed when sodium acetate is added to water?

CH3COOH

Which of the following mechanisms best describes the overall reaction CH4 + Cl2 → CH3Cl + HCl with an overall rate expression of rate = k [CH4][Cl2]?

CH4 + Cl2 → •CH3 + •Cl + HCl (slow) •CH3 + •Cl → CH3Cl (fast)

The reaction SbCl5 Cl2(g) + SbCl3 has a Keq of 3.2 x 10-6. Yet despite the small Keq when SbCl5 is dissolved and stirred in organic solvents for extended periods of time, unexpectedly high levels of solvated SbCl3 are measured in solution. Which of the following best explains this phenomenon?

Cl2(g) escapes from solution, driving the equilibrium toward SbCl3.

Based on the following half-reaction potentials, Sn4+(aq) + 2e- Sn2+(aq) E° = -0.14 V Ag+(aq) + e- Ag(s) E° = +0.80 V Cr3+(aq) + 3e- Cr(s) E° = -0.74 V Fe2+(aq) + 2e- Fe(s) E° = -0.44 V which of the following is the strongest reducing agent?

Cr(s)

The addition of 1 g of which of the following compounds to distilled water would cause the least change in pH?

CsOH

If the equation below represents an overall reaction in an electrochemical cell, which of the following materials likely constitutes the anode? 3 Cu(s) + 8 HNO3(aq) → 3 Cu(NO3)2(aq) + 2 NO(g) + 4 H2O(l)

Cu(s) The anode is the site of oxidation (an ox) and in the above reaction, copper is oxidized (loses an electron) from Cu(s) to Cu2+(aq) making Cu(s) the anode

Which of the following species is the oxidizing agent in the following redox reaction? Zn + Cu2+ Zn2+ + Cu

Cu2+

in the galvanic cell Ni|Ni2+||Fe3+, Fe2+|Pt, what best describes the direction of current flow and flow of Na+ from the salt bridge?

Current flows from Pt to Ni, and Na+ flows toward Pt. In electrochemical cells, electrons flow from anode to cathode In this cell, Ni2+ 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, allowing us to eliminate two answer choices. Na+ meanwhile travels from the salt bridge to the cathode to offset the charge imbalance generated by the current (cations migrate to the cathode).

In the galvanic cell Zn(s)|Zn2+(aq)||H+(aq)|H2(g)|Pt(s), the addition of excess Zn2+ to the solution at the Zn electrode will have what impact on the voltage?

Decrease as Q increases (as with addition of a product) the voltage decreases. Alternatively, we can relate this to Le Chatelier's principle. As we add more product, the reaction proceeds in reverse to a greater degree. Therefore the forward reaction becomes less spontaneous (voltage decreases) as a product is added.

All of the following statements regarding electrochemical cells are true

Electrolytic cells facilitate otherwise nonspontaneous reactions. Electric current always travels from cathode to anode in a galvanic cell. The electrode material at the anode of an electrochemical cell is corroded.

Using the following half-reaction potentials, Br2(l) + 2e- 2 Br-(aq) E° = 1.07 V F2(g) + 2e- 2 F-(aq) E° = 2.87 V determine the cell potential and whether the following reaction as written is spontaneous under standard conditions: 2 Br-(aq) + F2(g) Br2(l) + 2 F-(aq)

E° = +1.80 V, spontaneous

Which of the following is a contributing factor to the relative acidity of HF compared to HCl?

F- is less stable in solution than Cl-.

A battery stops functioning shortly after its initial use. What observation could explain the sudden failure of a battery?

Fracture of the anode/cathode barrier Breaking this barrier means electrons quickly transfer from reducing agent to oxidizing agent directly.. Solid formation at the cathode, etching visible on the anode, and color changes may be part of normal battery function, so we cannot be certain they resulted in battery death

The indicator bromothymol blue has a pKa near the pH of neutral water. Its basic form is a deep blue whereas its acidic form is a pale yellow. Near pH = 7 the indicator is green. If a solution of CsOH was slowly added to a solution of bromothymol blue in distilled water, what color change would be observed?

Green to blue

What is the Brønsted-Lowry base in the following reaction? HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)

H2O

Which of the following acids (in conjunction with an equal amount of its conjugate base) would be most appropriate to use in order to maintain a buffer solution of pH 7.4 at 25°C?

H2PO4- (pKa = 7.21)

Which of following acids would dissociate to the greatest degree?

H2SO3 (Ka = 1.4 x 10^-2) Given the Ka, which is an equilibrium constant, we can find the compound with the greatest degree of dissociation by looking for the largest Ka

A titration of which of the following aqueous hydrogen halides with NaOH will show an equivalence point above pH = 7?

HF

Which of the following is an amphoteric species?

HS- An amphoteric species is one that can act as either an acid or a base. The dissociation of hydrogen sulfide (H2S) is shown below:

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 11 L. If the reaction has proceeded for 2 hours at constant current, what was the value, in amps, of the current? (F = 96,500 C/mol)

I=Q/t 13.4 A 96,500/ (2*60*60)

If the solubility of AgCl in water is 1.3 × 10-4 mol/L, calculate the solubility product of AgCl.

If the solubility of AgCl in water is 1.3 × 10-4 mol/L, the solubility product of AgCl is 1.7 × 10-8. The equilibrium dissociation of AgCl is given by the equation AgCl(s) Ag+(aq) + Cl-(aq), so Ksp = [Ag+][Cl-]. If the concentration of dissolved AgCl is 1.3 × 10-4 M, then [Ag+] = [Cl-] = 1.3 × 10-4 M also. Therefore, Ksp = (1.3 × 10-4)2 = 1.7 × 10-8.

Which of the following best accounts for the difference in acid strength between H2S and H2Se?

Increased stability is observed in HSe- compared to HS-.

The following equilibrium exists in a closed container: N2(g) + O2(g) 2 NO(g) ΔH = +181 kJ/mol Which of the following perturbations would favor the formation of NO(g)?

Increasing the temperature

Which of the following would result in a change in the electrical potential of a galvanic cell consisting of solid silver and copper electrodes in solutions of their respective ions?

Increasing the temperature of the cell

Which of the following best describes a concentration cell?

It is a galvanic cell with two identical electrodes.

A radioactive nucleus decays by emitting a positron particle. What is true about the resulting daughter nucleus?

Its atomic number decreases.

A 1 M solution of which of the following compounds would have the lowest pOH?

KNH2 The anion of KNH2, NH2-, is a strongly basic anion, which will cause KNH2 solutions to be highly basic with low values of pOH.

Which of the following best characterizes the ionization constant of a strong acid?

Ka > 1

If a sample of barium hydroxide (Ba(OH)2) is partially dissolved in pure water at room temperature. If the equilibrium concentrations of Ba2+ and OH- ions are measured, which of the following expressions could be used to find the solubility product for barium hydroxide?

Ksp = [Ba][OH]^2

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?

Lewis acid

Red wines are generally acidic, with proper pH values near 3.6. At this pH, which of the following organic acids commonly found in wine have the highest proportion of molecules in the -1 charge-state? (note: pKa1 denotes the pKa of the most acidic proton on the compound; the pKa values of all subsequent protons on the compounds of interest are all near pH = 6)

Maleic acid (pKa1 = 1.90)

In an electrolytic cell containing molten MgCl2(l):

Mg2+ is reduced at the cathode, and Cl- is oxidized at the anode The anode is always the site of oxidation, and the cathode is always the site of reduction

Which of the following salts would yield acidic aqueous solutions when dissolved in water? NH4ClO4 AgNO3 NaC2H3O2

NH4ClO4 AgNO3

Ba(NO2)2 is a basic salt due to the interaction of the nitrite ion with water according to the following reaction: NO2- + H2O HNO2 + OH- Why does the equilibrium shown favor the left side of the reaction?

NO2− is a weaker base than OH−.

The molar solubility of HgCl2 in water is 0.27 M. If 0.1 mol of NaCl is added to 1 L of a 0.27 M aqueous solution of HgCl2, what will happen?

NaCl will dissolve and HgCl2 will precipitate.

n a fully charged NiCad battery, the anodic and cathodic reactions are as follows: Cd + 2 OH- → Cd(OH)2 + 2e- (anode) 2 NiO(OH) + 2 H2O + 2e- → 2 Ni(OH)2 + 2 OH- (cathode) Which of the following statements is true

Ni2+ is oxidized as the battery is recharged. Cd2+ is reduced as the battery is recharged. Cd is oxidized as the battery is discharged.

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?

Oxidation takes place at the positive electrode during recharging, but oxidation takes place at the negative electrode during discharging.

Enough HF (Ka = 7.4 × 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?

PbF2 PbF2 is essentially insoluble in water, and therefore will have the least effect on the pH, making it the best answer.

In a fully charged lead-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?

PbSO4 + 2e− → Pb

A potassium chloride salt bridge connects the two halves of an electrochemical cell. Which of the following best describes the path the salt bridge ions follow?

Potassium flows to the cathode, and chloride flows to the anode. alt bridges are responsible for neutralizing charge imbalance that results from the reaction occurring in a galvanic cell (or two-chamber electrolytic cell), so the cations and anions must travel to opposite electrodes.

Which of the following answer choices accurately describes the thermodynamics of the following reaction? (Keq = 0.5 at 25°C)

Reactants are favored at equilibrium and ΔG° will be greater than zero Given Keq < 1, reactants are favored at equilibrium, eliminating the choices written "products are favored..." If Keq < 1, then ΔG° will be greater than zero (non-spontaneous in the forward direction) according to the equation: ΔGº = -RTlnKeq.

The following two half-reactions occur in a voltaic cell: (1) Cr2O72-(aq) + 14 H+(aq) + 6e- 2 Cr3+(aq) + 7 H2O(l) (2) 6 I-(aq) 3 I2(s) + 6e- Which one of the following statements is true?

Reaction 2 is an oxidation and occurs at the anode. The anode is always the site of oxidation, and the cathode is always the site of reduction in any cell, so "Reaction 1 is a reduction and occurs at the anode" and "reaction 2 is an oxidation and occurs at the cathode" are wrong. In Reaction 2, it is clear that each I- anion must lose one electron in order for neutral I2 to be formed. The process of losing electrons is called oxidation, so the answer is "reaction 2 is an oxidation and occurs at the anode".

The conjugate bases of HSO4-, CH3OH, and H3O+ are, respectively:

SO42-, CH3O-, H2O

Based on the following data: Li+(aq) + e- Li(s) E° = -2.71 V Na+(aq) + e- Na(s) E° = -3.05 V which one of the following must be true?

Sodium metal is more easily oxidized than lithium metal. Flipping each of the reactions listed in the table reveals that Na(s) is more easily oxidized than Li(s), since 3.05 V > 2.71 V

According to the reduction potentials given above, Mn3+ is a much stronger oxidizing agent than Fe3+. However, one would expect that Fe3+ with its larger nuclear charge and slightly smaller size should gain electrons more easily than Mn3+. Which one of the following best accounts for this behavior?

The Mn3+ ion has a 3d4 electron configuration, and the gain of an electron to form Mn2+ gives the relatively stable 3d5 configuration. However, to convert Fe3+ to Fe2+ requires a change from a stable 3d5 configuration to a less stable 3d6 configuration.

When a catalyst is added to a chemical reaction, what will be its effect on the energy of the activated complex and on the rate of the reaction?

The energy of the activated complex will decrease, and the reaction rate will increase.

Which one of the following statements concerning 50 mL of basic solution composed of 0.2 M NaH2PO4 and 0.2 M Na2HPO4 is correct?

The pH of the solution will not change with the addition of 20 mL 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 this reading?

The reaction is spontaneous but the leads from the voltmeter to the anode and cathode have been reversed. The "lemon battery" must proceed via a spontaneous reaction or there would be no flow of current. An incomplete circuit would result in no electron flow. Therefore obtaining a negative reading must be due to a reversal of the leads.

The following reaction is allowed to reach equilibrium: Cl2O(g) + 2 OH-(aq) 2 OCl-(aq) + H2O(l) What will be the effect of then doubling the hydroxide concentration?

The reaction quotient will be one-fourth the equilibrium constant, favoring the forward reaction. Since the equilibrium constant, K, and the reaction quotient, Q, are inversely proportional to [OH-]2, doubling [OH-] will cause K to decrease by a factor of 22 = 4. Thus, the reaction quotient, Q, will be one-fourth of K, favoring the forward reaction.

Consider the reaction . At equilibrium, a 10 L vessel contains 1.5 moles of HI, 0.1 moles of I2 and 0.3 moles of H2. Which direction will the reaction proceed if 2 moles of HI, and 0.5 moles of both I2 and H2 are mixed in a separate 10 L vessel?

The reaction will proceed forward.

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?

The reduction potential of cationic gold is larger than that of cationic iron.

What is the relationship between the mass of an atom and the sum of the masses of its constituent particles?

The sum of the masses of the constituent particles is greater. from Einstein's equation, E = mc^2, this difference in energy translates into a mass defect in the bound atom (albeit a very small difference). In other words, the mass of the atom is smaller than the sum of the masses of its constituent atoms because the energy of the bound atom is smaller than the individual particles.

Which of the following statements about stable chemical isotopes is true

Theoretical rate constants of decay are very small. Many stable isotopes are naturally occurring. Isotopes can be separated by both chemical and physical means. Changing the number of neutrons directly affects nuclear stability, particularly for lighter elements.

Which of the following statements is true about a solution of acetic acid in equilibrium? CH3CH2COOH (aq) H+ (aq) + CH3CH2COO- (aq)

When HCl is added, CH3CH2COO- acts as a Brønsted-Lowry base.

The addition of a catalyst to a chemical reaction will bring about:

a decrease in activation energy and an increase in the rate of the forward reaction.

A salt solution contains ammonium cation (Ka = 5.7 × 10-10) and nitrite anion (Kb = 1.4 × 10-11) in equal proportions. The pH of the solution will be:

acidic because ammonium has a higher Ka value than the Kb of nitrite.

Each of the following are true of redox titrations

at the half-equivalence point, the concentrations of the oxidized and reduced form of the analyte are equal. the reaction occurring during the titration involves the transfer of electrons between the titrant and analyze. at the equivalence point, the reaction between the analyte and titrant is complete.

A β- particle is emitted by a lithium nucleus. The resulting nucleus will be an isotope of:

beryllium. The result of beta decay is the transformation of a neutron to a proton and an expelled electron (β- particle). Therefore, the atomic number increases by one. So, if the original atom was lithium (Z = 3), the daughter atom will be beryllium (Z = 4).

4-Nitrophenol (pKa = 7.08) is an indicator that is yellow when deprotonated and colorless when protonated in solution. If a solution has a pOH of 10, its color will be:

colorless.

N2(g) + 3 H2(g) 2 NH3(g), ΔH = -22 kcal/mol Increasing the temperature of the reaction at equilibrium will most likely:

decrease the forward reaction.

Addition of sodium acetate to a solution of acetic acid will cause the pH to:

increase due to the common ion effect. Sodium acetate is a basic compound,

If carbon dioxide gas is in equilibrium with an aqueous solution of carbonic acid, then the CO2 solubility can be increased by:

increasing the pressure.

Strong reducing agents readily Al3+ + 3e- Al E° = -1.67 Au3+ + 3e- Au E° = +1.50

lose electrons and are easily oxidized. Likewise, strong oxidizing agents readily gain electrons and are easily reduced. In the half reactions shown, Al3+ gains electrons (is reduced), but the reduction potential for the reaction is negative, indicating it is not spontaneous. Therefore Al3+ is not a good oxidizing agent. Since Au3+ is shown spontaneously gaining electrons (positive E°), not losing them, it cannot be a reducing agent.

When an element is oxidized, it will:

lose electrons, and its oxidation state will increase.

When CaF2 is added to a 0.02 M solution of NaF, the solubility of CaF2 is:

low, because the concentration of F- already present in solution prevents dissolution of CaF2.

An electrolysis experiment compares the effects of using various salts in aqueous solutions. Compared with Na, K has a:

lower ionization energy and is a better reducing agent. Since K is a better reducing agent, it will lose electrons more easily and have a lower ionization energy compared with Na.

In an electrolytic cell, the electrochemical reaction is:

nonspontaneous, with oxidation occurring at anode. Electrolytic cells involve nonspontaneous chemical reactions, since the anode is the site of oxidation (and the cathode the site of reduction) in any electrochemical cell, the answer is "nonspontaneous, with oxidation occurring at anode".

In the formation of CO2 through the reaction of O2 and C(s), graphite acts as a(n):

reducing agent

Since Q < K

the forward reaction is favored.

A sealed container contains NO2, a brownish-red gas, and N2O4, a colorless gas, at equilibrium at 0°C according to the following reaction: . How will the color of the gas mixture change if the container is placed in dry ice and acetone at -78°C?

the gas mixture will become lighter in color.

Which of the following are advantageous properties for a titrant to have in a redox titration?

the net electrochemical reaction must have positive electric potential. The titrant must be able to be standardized or exist in a pure solid form the reaction must be spontaneous for the titration to occur, meaning ΔG must be negative and Eo must be positive.

Since E° is positive,

the reaction is spontaneous.

Consider the following reduction reactions and their standard potentials: Cu2+ + 2e- → Cu(s) E° = +0.337 V Zn2+ + 2e- → Zn(s) E° = -0.763 V If a piece of Zn metal is dropped into a CuSO4(aq) solution, and a piece of Cu metal is dropped into a ZnSO4(aq) solution, then

the zinc metal will begin to dissolve in CuSO4 solution since Zn(s) is a stronger reducing agent than Cu(s). The voltages given for these redox half-reactions indicate that Cu2+ likes to be reduced, but Zn2+ doesn't. Therefore, Zn metal will be oxidized in CuSO4 solution—so Zn metal is the reducing agent—and Cu would precipitate out. The net ionic equation is Zn(s) + Cu2+ → Cu(s) + Zn2+.

A sample of solid Mg(OH)2 is added to water and reaches equilibrium with its dissociated ions. Addition of the strong base NaOH would most notably increase the concentration of:

undissociated magnesium hydroxide.

The [Pb2+] of a solution is 1.25 × 10-3 M. Calculate the [SO42-] that must be exceeded before PbSO4 can precipitate. (The solubility product of PbSO4 at 25°C is 1.6 × 10-8.)

we have Ksp = [Pb2+][SO42-]. Therefore, the minimum concentration of SO42- needed to form precipitate is [SO42-] = Ksp/[Pb2+] = (1.6 × 10-8)/(1.25 × 10-3) = 1.3 × 10-5 M.

If Keq for a given reaction is large in standard state conditions, which of the following is necessarily true about the thermodynamic parameters of the reaction?

ΔG˚ is negative

Which of the following is necessarily true for any reaction at equilibrium?

ΔH = TΔS

Which of the following is emitted in the conversion of 11C 11B?

β+ particle