chem 104 exam 1

A 500-mL sample of argon at 800 mmHg has its absolute temperature quadrupled. If the volume remains unchanged, what is the new pressure? A) 200 mmHg B) 400 mmHg C) 800 mmHg D) 2400 mmHg E) 3200 mmHg

E

A small bubble rises from the bottom of a lake, where the temperature and pressure are 277 K and 3.0 atm, to the water's surface, where the temperature is 298 K and the pressure is 0.95 atm. Calculate the final volume of the bubble if its initial volume was 2.1 mL. A) 0.72 mL B) 6.2 mL C) 41.4 mL D) 22.4 mL E) 7.1 mL

E

Water can act as a A) weak acid. B) strong acid. C) weak base. D) strong base. E) two of the above.

E

What is the difference between a strong acid and a weak acid? A) a strong acid contains strong covalent bonds whereas a week acid does not B) a strong acid has more hydrogen atoms in its molecule than a weak acid C) a weak acid is nonpolar, whereas a strong acid is polar D) strong acids react with both strong and weak bases, whereas weak acids do not E) none of the above

E

What is the freezing point of a solution prepared from 50.0 g (NH4)2SO4 (132.14 g / mol) and 85.0 g H2O? For water, Kf is 1.86 °C / m and Kb is 0.512 °C / m. A) 24.8°C B) -8.28°C C) -16.6°C D) 8.28°C E) -24.8°C

E

explain the period and group trend for atomic radii in terms of effective nuclear charge and increasing shell size.

Period: Effective nuclear charge (Zeff) increases as non-metallic character increases (moving left to right in the periodic table). Because the proton number is increasing while the shell number remains unchanged, there is a stronger force of attraction pulling the electrons closer towards the nucleus, making the atomic radius decrease as the group number increases. Group: The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase.

Consider the hybridization of each carbon atom in ethane (C2H4, aka ethylene). Describe the promotion and hybridization steps required for carbon to achieve this state of hybridization molecule.

The carbon atoms need to be sp2 hybridized, leaving the 2pz orbital on each carbon unhybridized. Overlap of one sp2 hybrid on each carbon and occupation of this region by an electron pair produces a C-C sigma bond. Overlap of the remaining four hybrid orbitals with 1s orbitals of four hydrogen atoms, produces four C-H sigma bonds. The unhybridized 2pz orbitals overlap laterally to produce a pi bond which has two regions of electron density, above and below the C-C sigma bond. (Diagram needed.) Carbon 2s ^ v 2p ^ ^ _ --> PROMOTION 2s ^ 2p ^ ^ ^ --> HYBRIDIZATION sp3 and angles are 109.5

After synthesizing some aspirin via an esterification of salicylic acid, you use a ferric chloride test to analyze your product. If your sample does not turn purple (indicating an absence of phenol), which of the follow can you conclude?

Your product does not contain any salicylic acid.

The value of the equilibrium constant is not affected by the concentrations of A) pure solids and liquids. B) gases. C) aqueous solutions. D) all of the above.

A

Which of the following is (are) unaffected by reversing the direction in which a chemical equation is written? A) The equilibrium concentrations B) The equilibrium constant value C) The mass action expression D) All of the above

A

Case 1: Solution A: 0.10 M KCl or Solution B: 0.20 M MgCl2 A. Towards A B. Towards B C. Neither

B

The hydroxide ion is the conjugate base of the hydronium ion. A) True B) False

B

Calculate the mass in grams of 0.0504 moles of an acid having the molar mass equal to 100.5. A) 5.1 B) 19.84 C) 5.07 D) 5.065 E) none of the above

C

Chemical reactions take place because the molecules involved in a reaction A) break apart spontaneously, then recombine. B) exist only above a certain temperature. C) collide with each other and break bonds. D) are moving very fast. E) are very unstable.

C

Which of the following will produce a basic solution when dissolved in water? A) Na2O B) NaOH C) Both A and B D) None of the above

C

The Arrhenius equation is k = Ae-Ea/RT. The slope of a plot of ln k vs. 1/T is equal to A) -k B) k C) Ea D) -Ea /R E) A

D

The chloride ion in aqueous solution is a A) strong conjugated acid. B) weak conjugated acid. C) strong conjugated base. D) weak conjugated base.

D

Determine the half-life for a reaction that has a rate constant of 0.0260 min-1. A) 18.5 min B) 38.5 min C) 9.250 min D) 19.3 min E) 26.7 min

E

Which pair of compounds will form a buffer solution when dissolved in water in equimolar amounts? HCl and KCl HNO3 and NaNO3 HCl and NH4Cl NH3 and NH4Cl

NH3 and NH4Cl

When the phase diagram for a substance has a solid-liquid phase boundary line that has a negative slope (leans to the left), the substance ________

can go from solid to liquid, within a small temperature range, via the application of pressure

What type(s) of intermolecular forces exist between Cl2 and CO3^-2 ?

dispersion forces and ion-induced dipole

Which of the following are buffer systems? (a) KF/HF (b) KBr/HBr, (c) Na2CO3/NaHCO3

(a) KF is a weak acid and F- is its conjugate base buffer soln (b) HBr is a strong acid not (c) CO32- is a weak base and HCO3- is its conjugate acid buffer soln

For questions 5 & 6, please consider the following scenario. A semipermeable membrane separates two aqueous solutions at 20 °C. For each of the following cases, name the solution into which a net flow of water (if any) will occur. Assume 100% dissociation for electrolytes.

...

Calculate the pH of a 0.018M solution of Ca(OH)2. A) 12.56 B) 1.8 C) 1.44 D) 12.25 E) none of the above

A

Consider the following reaction: CaCO3(s) ↔ CO2(g) + CaO(s) . What will happen to the system if more CaCO3 is added? A) nothing B) the amount of CaCO3 will decrease C) less CaO will be produced D) the pressure will increase E) the concentration of CO2 will decrease

A

Consider the reaction of hydrogen gas and oxygen gas to produce liquid water. Which of the following is true? A) The position of the equilibrium is unaffected by the addition of liquid water. B) Removing some of the hydrogen gas has no effect on the position of the equilibrium. C) Reducing the volume of the reaction vessel has no effect on the position of the equilibrium. D) None of the above are true.

A

If a reaction is endothermic, then the equilibrium constant is higher at higher temperature. A) True B) False

A

What is the molar mass of the nonelectrolyte toluene, a common octane booster in gasoline, if 0.850 g of toluene depresses the freezing point of 100. g of benzene by 0.470 °C? Kf of benzene is 5.12 °C kg / mol. A) 92.6 g/mol B) 78.0 g/mol C) 10.7 g/mol D) 81.8 g/mol E) 927 g/mol

A

What will be the pH of a 1.0 × 10-8 M solution of HCl? A) 8.0 B) 6.0 C) cannot be calculated D) it will be slightly less than 7.0 E) it will be slightly more than 7.0

A

Which of the following is a neutral salt (neither acidic nor basic)? A) KCl B) NaCN C) NH4NO3 D) NaF

A

What are important differences in comparing the properties of pi and sigma bonds, in terms of how they affect the structure and reactivity of molecules? To describe these differences, List at least one physical and one chemical difference.

A sigma bond is stronger than a pi bond, making pi bond more reactive. There is free rotation about a sigma bond but not about a pi bond, giving rise to the possibility of geometrical isomers in the latter case. (Sigma bonds are one bond, typically single. A single bond has one sigma bond. A pi bond is # of bonds-sigma bonds. A double bond has 1 sigma bond and 1 pi bond while a triple bond has 1 sigma bond and 2 pi bonds. Sigma bonds are head to head and have cylindrical symmetry. Pi bonds are side to side and weaken with greater electron density)

A reaction that has a very high activation energy A)has a rate that does not change much with temperature. B)has a rate that is very sensitive to temperature. C)must be first-order. D)must be second-order. E)gives a curved Arrhenius plot.

B

Consider the chemical change AÛB. After the reaction starts, but before the system reaches equilibrium, the only process that takes places is A being converted into B. A) True B) False

B

Consider the following reaction: 2H2(g) + 2Cl2(g) ↔ 2HCl(g) + heat . What will happen to the system if the volume of the reaction vessel is decreased? A) more HCl will dissociate B) amounts of H2 and Cl2 will decrease C) less heat is produced D) all of the above E) none of the above

B

Consider the following reaction: 4HCl(g) + O2(g) ↔ 2H2O(g) + 2Cl2(g) with DH = -114.4 kJ One way to decrease the amount of chlorine present at equilibrium is A) removing the water vapor while it is being formed. B) raising the temperature. C) adding more hydrogen chloride. D) decreasing the volume of the reaction vessel. E) none of the above.

B

The value of an equilibrium constant depends on A) the rate of the reaction. B) how the equilibrium equation is balanced. C) the starting concentrations of the reactants. D) all of the above.

B

Which is true regarding the equilibrium below? HF(g) + H2O(l) ↔ F- + H3O+(aq) A) HF is acting as a Bronsted base. B) Water is acting as a Bronsted base. C) The reaction goes to completion leaving little HF. D) The Fluoride ion is acting as Bronsted acid.

B

Which of the following best describes the acid strengths of the hydrohalic acids? A) HF>HCl>HBr>>HI B) HF<<HCl<HBr<HI C) HF=HCl=HBr=HI D) HF=HCl<HBr=HI

B

Which of the following liquids would make a good solvent for octane, C8H18? A) HCl B) C6H6 C) CH3OH D) NH3 E) H2O

B

Which pH region is most likely for a sample of vinegar? A) 0 to 1 B) 1 to 6 C) 8 to 13 D) 13 to 14 E) none of the above

B

A Lewis base is a(an) A) substance that contains the hydroxide ion. B) proton acceptor. C) electron pair donor. D) none of the above

C

Arrange the following 0.1 m aqueous solutions in order of increasing boiling points: A)Mg(NO3)2 < NaCl <ethanol B)ethanol < Mg(NO3)2 <NaCl C)ethanol <NaCl< Mg(NO3)2 D)NaCl < ethanol < Mg(NO3)2 E)Mg(NO3)2 < ethanol < NaCl

C

Calculate the equilibrium constant for the process A-->B, given the following equilibrium concentrations: [N2O4] = 0.0427 M ; [NO2] = 0.0141 M A) 6.60x10-1 B) 215 C) 0.00466 D) 0.330 E) 3.03

C

Case 2: Solution A: 0.10 M Al(NO3)3 or Solution B: 0.20 M NaNO3 A. Towards A B. Towards B C. Neither

C

Consider a solution made from a nonvolatile solute and a volatile solvent. Which statement is true? A)The boiling point of the solution will be lowered relative to the pure solvent. B)The osmotic pressure of the solution will be lowered relative to the pure solvent. C)The vapor pressure of the solution will be lowered relative to the pure solvent. D)The freezing point of the solution will be greater relative to the pure solvent. E)None of the prior statements are true in this case.

C

For a particular set of concentrations, if the value of Q is much greater than the value of the equilibrium constant, K, for a reaction, then A) the initial rate of the reaction will be very fast, but will slow as equilibrium is approached. B) the reaction will proceed to the right, but the rate cannot be determined from the Q or K. C) the reaction will proceed to the left, but the rate cannot be determined from the Q or K. D) the reaction will proceed to make more products if the value of K is much greater than one.

C

If an equilibrium for a reaction is said to lie to the right then the equilibrium constant A) is a negative value. B) is a positive value less than one. C) is a positive value greater than one. D) is equal to one.

C

In a solution, the solvent: A) is a liquid. B) can be a liquid or gas. C) can be a solid, liquid, or gas. D) is never a solid. E) is the substance present in the smallest concentration.

C

Spock adds 0.1016 g of an unknown gas to a 125-mL flask. If Spock finds the pressure to be 736 mmHg at 20.0 °C, is the gas likely to be methane, CH4, nitrogen, N2, oxygen, O2, neon, Ne, or argon, Ar? A) CH4 B) N2 C) Ne D) Ar E) O2

C

The concentrations of pure solids are normally excluded in an equilibrium constant expression because A) these substances do not participate in the processes that are at equilibrium. B) at the time the equilibrium is established, their absolute amounts have not varied from the original amounts. C) the concentration of a pure solid remains essentially constant throughout the reaction. D) they do not play a vital role in the rate-determining step of the reaction. E) none of the above.

C

When KOH and HNO3 are mixed, a reaction occurs. What are the spectator ions in the reaction? A) K+ and H+ B) H+ and OH- C) K+ and NO3- D) H+ and NO3- E) there are no spectator ions in this reaction

C

Which of the following has an impact on the percent ionization of a weak acid? A) The acid ionization constant. B) The concentration of the acid. C) Both A and B. D) None of the above.

C

Which of the following is(are) true? A) pH can never be greater than 14. B) pH can never be less than 0. C) At room temperature, pH + pOH =14. D) All of the above.

C

Which of the following salts is expected to produce a basic solution upon hydrolysis? A) calcium chloride B) ammonium sulfate C) sodium acetate D) ammonium acetate E) ferrous bromide

C

Which one of the following units is not an acceptable way to express reaction rate? A) M/s B) M * min-1 C) L * mol-1 * s-1 D) mol * L-1 * s-1 E) M/hr

C

At equilibrium A) the rate constants for the forward and reverse reactions are equal. B) the reaction ends. C) all reactants have been converted to products. D) the forward and reverse rates are equal. E) none of the above.

D

For reactions in gas phase, a relationship can be established between Kc and Kp. For which of the following processes will the two constants have the same numerical value? A) formation of water vapor from hydrogen and oxygen B) formation of carbon dioxide from carbon monoxide and oxygen C) synthesis of ammonia from hydrogen and nitrogen D) decomposition of hydrogen iodide into hydrogen and iodine gas E) conversion of nitrogen dioxide into dinitrogen tetroxide

D

In a 0.100 M solution of sodium hydroxide, what are the equilibrium concentrations of sodium hydroxide, sodium ions, hydroxide ions, and hydronium ions, respectively? A) 0.100; 0.100; 0.100; 0 B) 0.100; 0.100; 0.100; 1X10^-13 C) 0; 0.100; 0.100; 0 D) 0; 0.100; 0.100; 1X10^-13

D

Lithium oxide is an effective absorber of carbon dioxide and can be used to purify air in confined areas such as space vehicles. What volume of carbon dioxide can be absorbed by 1.00 kg of lithium oxide at 25°C and 1.00 atm? Li2O (aq) + CO2 (g) Li2CO3(s) A) 687 mL B) 819 mL C) 687 L D) 819 L E) 22.4 L

D

The reaction N2O4(g) ↔ 2NO2(g) is endothermic. Which of the following is true? A) Decreasing the pressure drives the reaction to the right. B) Increasing the temperature drives the reaction to the right. C) Decreasing the volume drives the reaction to the left. D) All of the above.

D

The reaction of hydrogen gas with nitrogen gas to produce ammonia gas is exothermic. Which of the following is true? A) Increasing the pressure of the reaction system will increase production of ammonia. B) Condensing the ammonia gas produced into liquid will increase the production of ammonia. C) Decreasing the temperature of the reaction will increase the production of ammonia. D) All of the above.

D

The reaction of oxygen with hemoglobin produces oxyhemoglobin, which carries oxygen to body tissues. At high altitudes the following results are seen A) the lower oxygen pressure causes the equilibrium to shift away from oxyhemoglobin. B) "altitude sickness" can occur in unacclimated individuals. C) people who live in higher altitudes develop higher levels of hemoglobin to function normally. D) all of the above.

D

The substance that is largely responsible for acid rain is A) calcium carbonate. B) sodium chloride. C) ozone. D) sulfur dioxide.

D

Which of the following concentration units is temperature dependent? A)Mole fraction B)Molality C)Mass percent D)Molarity E)None of the above - all concentration units are independent of temperature

D

Which of the following statements is true of a catalyst? A) Its concentration stays constant throughout the reaction B) it increases the rate of a reaction C) it provides a new pathway for the reaction D) all of the above E) none of the above

D