Chem final review

Calculate DS° for the dissociation of dinitrogen tetraoxide at 25°C. N2O4(g) ® 2NO2(g) Substance Gf(kJ/mol) Hf(kJ/mol) NO2(g) +51.3 +33.2 N2O4(g) +97.9 +9.2 Select one: a. -2.10 kJ/K b. +2.10 kJ/K c. -0.550 kJ/K d. +0.176 kJ/K e. -0.208 kJ/K

+0.176 kJ/K

calculate delta S for the following reaction H2(g) + Br2(l) -> 2HBr(g) given S[H2] = +131 J/molK, S[Brs(l)] = +152 J/molK and S[HBr(g)] = +199J/mol a. +115 J/K b. -84 J/K c. +681 J/K d. +84 J/K e. +482 J/K

+115 J/K

Calculate delta Gf at 325 K for ethylene, C2H4(g), given the thermodynamic data below. Substance dHf S° (kJ/mol×K) C(s) 0.0 +0.0057 H2(g) 0.0 +0.1306 C2H4(g) +52.3 +0.2195

+69.6 kJ

Ammonia is synthesized from nitrogen and hydrogen gases at a temperature of 475°C. N2(g) + 3H2(g) ® 2NH3(g) If DH° = -92.2 kJ and DS° = -0.1987 kJ/K, what is DG° for the reaction at 575°C? Select one: a. +2.2 kJ b. -92.0 kJ c. +76.3 kJ d. -186.6 kJ e. -260.7 kJ

+76.3 kJ

Given that, at 25°C, C(s) + O2(g) ® CO2(g) DG° = -394.4 kJ C(s) + (1/2)O2(g) ® CO(g) DG° = -137.2 kJ calculate DG° for the reaction below. CO(g) + (1/2)O2(g) ® CO2(g) Select one: a. -171.5 kJ b. +531.6 kJ c. +141.2 kJ d. -257.2 kJ e. -531.6 kJ

-257.2 kJ

For the dimerization of nitrogen dioxide, DG° = -4.7 kJ at 25°C. 2NO2(g) ® N2O4(g) Calculate DG for this reaction if the partial pressures of NO2 and N2O4 are both 0.50 atm. (R = 8.31 ´ 10-3 kJ/K) Select one: a. -3.0 kJ b. -4.6 kJ c. -4.7 kJ d. -6.4 kJ e. -4.8 kJ

-3.0 kJ

Calculate DG° for the following reaction at 298 K. S(s) + O2(g) ® SO2(g) Substance Hf S° (kJ/mol×K) S(s) 0.0 +0.0318 O2(g) 0.0 +0.2050 SO2(g) -296.8 +0.2481 Select one: a. +29.3 kJ b. -300.2 kJ c. -296.8 kJ d. +145.7 kJ e. -85.1 kJ

-300.2 kJ

Calculate DG° for the reaction below at 25.0°C. P4O10(s) + 6H2O(l) ® 4H3PO4(l) Species Hf S° (J/mol×K ) P4O10(s) -2984.0 228.9 H2O(l) -285.8 69.95 H3PO4(l) -1279.0 110.5 a. +6119.1 kJ b. -355.6 kJ c. +210.6 kJ d. -6119.1 kJ e. -632.8 kJ

-355.6 kJ

Given that S(g) + O2(g) ® SO2(g) DG° = -300.1 kJ 2S(g) + 3O2(g) ® 2SO3(g) DG° = -742.1 kJ calculate mc051-1.jpg of the following reaction: SO2(g) + 1/2O2(g) ® SO3(g) Select one: a. +2.47 kJ b. -71.0 kJ c. +1042.2 kJ d. +71.0 kJ e. -1042.2 kJ

-71.0 kJ

The following processes occur spontaneously at 25°C. Which of these processes is/are endothermic? 1. NH4NO3 dissolving in water (which is accompanied by a cooling of the water). 2. the expansion of a real gas into a vacuum (which is accompanied by a cooling of the gas). 3. liquid water in an ice cube tray freezing into ice after being placed in a freezer. Select one: a. 1 only b. 1 and 2 c. 3 only d. 2 only e. 1, 2, and 3

1 and 2 only

For the decomposition of calcium carbonate, DG° = +130.4 kJ at 25°C. CaCO3(s) ® CaO(s) + CO2(g) Calculate the partial pressure of CO2 if DG = 0.0 kJ. (R = 8.31 ´ 10-3 kJ/K) Select one: a. 2.7 ´ 10^2 atm b. 5.3 ´ 10^1 atm c. 1.3 ´ 10^-23 atm d. 8.2 ´ 10^-5 atm e. 7.4 ´ 10^22 atm

1.3*10^23 atm

The standard free energy change associated with the dissolution of ammonium nitrate in water is -6.73 kJ at 298 K. NH4NO3(s) = NH4NO3(aq) what is the equilibrium constant for the reaction? a. 15 b. 6.6 ´ 10^-2 c. 1.0 d. 1.9 ´ 10^-3 e. 5.2 ´ 10^2

15

For which of the following reactions will the entropy of the system decrease? Select one: a. 2NO2(g) -> N2O4(g) b. CaCO3(s) -> CaO(s) + CO2(g) c. 2C(s) + O2(g) -> 2CO(g) d. NaOH(s) -> Na+(aq) + OH-(aq) e. 2NH3(g) -> N2(g) + 3H2(g)

2NO2(g) -> N2O4(g)

Which of the following statements concerning entropy is/are CORRECT? 1. The entropy of a substance increases when converted from a liquid to a solid. 2. The entropy of a substance decreases as its temperature increases. 3. All substances have positive standard molar entropies at temperatures above 0 K. Select one: a. 3 only b. 2 only c. 1 and 2 d. 1 only e. 1, 2, and 3

3 only

Ammonia is synthesized from nitrogen and hydrogen gases. N2(g) + 3H2(g) ® 2NH3(g) If DH° = -92.2 kJ and DS° = -0.1987 kJ/K, at what temperature will DG° = 0? Select one: a. 92.0 K b. 0.00216 K c. 672 K d. 18.3 K e. 464 K

464 K

At 25°C, the equilibrium constant for the following reaction, Cu2+(aq) + Zn(s) ® Cu(s) + Zn2+(aq) is 1.9 ´ 1037. Calculate DG° for this reaction. (R = 8.31 ´ 10-3 kJ/K) Select one: a. -145 kJ b. +57.3 kJ c. -213 kJ d. -57.3 kJ e. +213 kJ

C -213 kJ

Which of the following linear chain alcohols is likely to have the largest standard molar entropy in the liquid state? Select one: a. CH3CH2CH2CH2CH2OH b. CH3OH c. CH3CH2OH d. CH3CH2CH2OH e. CH3CH2CH2CH2OH

CH3CH2CH2CH2CH2OH

When a real gas is compressed from low pressure to a higher pressure, its temperature increases. Predict the signs of DH and DS. Select one: a. DH < 0 and DS = 0 b. DH < 0 and DS < 0 c. DH < 0 and DS > 0 d. DH > 0 and DS < 0 e. DH > 0 and DS > 0

DH < 0 and DS < 0

If DG is negative at all temperatures, then which of the following statements must be true? Select one: a. DH > 0 and DS < 0 b. DH < 0 and DS = 0 c. DH > 0 and DS > 0 d. DH < 0 and DS > 0 e. DH < 0 and DS < 0

DH < 0 and DS > 0

Diluting concentrated sulfuric acid with water can be dangerous. The temperature of the solution can increase rapidly. What are the signs of DH, DS, and DG for this process? a. DH < 0, DS > 0, DG < 0 b. DH > 0, DS > 0, DG < 0 c. DH < 0, DS < 0, DG < 0 d. DH < 0, DS > 0, DG > 0 e. DH > 0, DS < 0, DG > 0

DH < 0, DS > 0, DG < 0

what is the correct form for the Gibbs-Helmholtz equation? a. DG = DH + TDS b. DG = DH - TDS c. DH = DG - TDS d. DG = DS - TDH e. DS = DH - TDG

Delta G = Delta H - T Delta S

If DG° = 0, then Select one: a. K < -1. b. K = 1. c. K < 1. d. K < 0. e. K = 0.

K=1

In what temperature range is DG° greater than zero for the formation of NH4Cl(s) from NH3(g) and HCl(g)? NH3(g) + HCl(g) ® NH4Cl(s) For the reaction, DH° = -176.0 kJ and DS° = -0.2845 kJ/K. Select one: a. The temperature must be less than 619 K. b. The temperature must be greater than 619 K. c. The temperature must be exactly 619 K. d. DG° is always greater than zero. e. DG° is never greater than zero.

The temperature must be greater than 619 K.

At 25°C, the acid dissociation constant for formic acid is 6.9 ´ 10-4. Calculate DG° for this reaction. (R = 8.31 ´ 10-3 kJ/K) Select one: a. +18.0 kJ b. +1.51 kJ c. -18.0 kJ d. -1.51 kJ e. +41.4 kJ

a. +18.0 kJ

All of the following statements are false for the freezing of water at 273 K EXCEPT Select one: a. DH < 0. b. DH > 0. c. DS > 0. d. DH = 0. e. DS = 0.

a. DH < 0.

The dissolution of ammonium nitrate occurs spontaneously in water at 25°C. As NH4NO3 dissolves, the temperature of the water decreases. What are the signs of DH, DS, and DG for this process? Select one: a. DH > 0, DS > 0, DG < 0 b. DH < 0, DS > 0, DG > 0 c. DH > 0, DS > 0, DG > 0 d. DH > 0, DS < 0, DG > 0 e. DH < 0, DS < 0, DG < 0

a. DH > 0, DS > 0, DG < 0

All of the following events result in an increase in entropy EXCEPT Select one: a. the formation of N2O4(g) from NO2(g). b. the combustion of carbon. c. the melting of candle wax. d. the evaporation of ethanol. e. the dissolution of sodium chloride in water.

a. the formation of N2O4(g) from NO2(g).

For a chemical reaction, DG and DG° are equal Select one: a. when products and reactants are in standard state concentrations. b. for a system at equilibrium. c. when K = 0. d. when K > 1. e. when the entropy change is zero.

a. when products and reactants are in standard state concentrations.

Calculate DS° for the dissolution of BaCl2 in water at 25°C. BaCl2(s) ® Ba2+(aq) + 2Cl-(aq) Substance Gf Hf BaCl2(s) -810.4 -858.6 Ba2+(aq) -560.8 -537.6 Cl-(aq) -131.2 -167.2 Select one: a. -0.20 kJ/K b. -0.0020 kJ/K c. +0.29 kJ/K d. +0.12 kJ/K e. -0.14 kJ/K

b. -0.0020 kJ/K

If a chemical reaction is exothermic, but not spontaneous, which of the following must be true? Select one: a. DG > 0, DS > 0 and DH > 0 b. DG > 0, DS < 0 and DH < 0 c. DG > 0, DS < 0 and DH > 0 d. DG < 0, DS < 0 and DH < 0 e. DG < 0, DS > 0 and DH > 0

b. DG > 0, DS < 0 and DH < 0

The third law of thermodynamics states that Select one: a. the total entropy of the universe is always increasing. b. there is no disorder in a perfect crystal at 0 K. c. in a spontaneous process, the entropy of the universe increases. d. the total mass of the universe is constant. e. mass and energy are conserved in all chemical reactions.

b. there is no disorder in a perfect crystal at 0 K.

The standard free energy change for a chemical reaction is +13.3 kJ. What is the equilibrium constant for the reaction at 125°C? (R = 8.31 ´ 10-3 kJ/K) Select one: a. 2.8 ´ 10-6 b. 2.0 ´ 10-5 c. 1.8 ´ 10-2 d. 2.1 ´ 102 e. 4.7 ´ 10-3

c. 1.8 ´ 10-2

Rubber elasticity is an entropic phenomenon. As a rubber band is stretched the entropy of the system Select one: a. breaks the polymer chain. b. is increased. c. is reduced. d. remains unchanged. e. causes chemical bonds to form.

c. is reduced

Nitric oxide can be made from the reaction of oxygen and nitrogen gases. O2(g) + N2(g) ® 2NO(g) If DG° = 165.5 kJ, and DH° = 180.4 kJ, what is DS° at 325°C? Select one: a. 0.0125 kJ/K b. 0.0458 kJ/K c. 1.02 kJ/K d. 0.0249 kJ/K e. 0.142 kJ/K

d. 0.0249 kJ/K

Which of the following reactions is likely to have the most positive change in entropy? Select one: a. CaO(s) + CO2(g) ® CaCO3(s) b. C(s) + O2(g) ® CO2(g) c. N2(g) + 2O2(g) ® 2NO2(g) d. 2C(s) + O2(g) ® 2CO(g) e. N2(g) + 3H2(g) ® 2NH3(g)

d. 2C(s) + O2(g) ® 2CO(g)

In a gas phase reaction, what is the effect of increasing reactant or product pressure on the standard Gibbs free energy, DG°? Select one: a. DG° may either increase or decrease. b. DG° decreases due to decreased entropy. c. DG° increases due to decreased entropy. d. DG° is unchanged. e. DG° increases due to increased enthalpy.

d. DG° is unchanged.

Predict the signs of DS and DH for the evaporation of water at 295 K. Select one: a. DH < 0 and DS < 0 b. DH = 0 and DS > 0 c. DH > 0 and DS < 0 d. DH > 0 and DS > 0 e. DH < 0 and DS > 0

d. DH > 0 and DS > 0

All of the following statements are true EXCEPT Select one: a. a reaction is spontaneous if DG < 0. b. if DG > 0, then a reaction is not spontaneous. c. DG is referred to as Gibbs free energy. d. if DG = 0, then DS = DH. e. if DG = 0, the system is at equilibrium

d. if DG = 0, then DS = DH.

All of the following statements are true EXCEPT Select one: a. DH < 0 for exothermic reactions. b. DS > 0 for systems that become more disorderly. c. reactions are spontaneous when DG < 0. d. reactions are spontaneous when DH < 0. e. generally, nature tends to move from more ordered to more random states.

d. reactions are spontaneous when DH < 0.

Which of the following are conditions for the standard Gibbs free energy? 1. Ions or molecules in solution are present at one molar concentrations. 2. Gases are present at one atmosphere partial pressure. 3. The temperature of the system is 273 K. Select one: a. 3 only b. 1 only c. 1, 2, and 3 d. 2 only e. 1 and 2

e 1 and 2

Calculate DG° for the reaction below at 25.0°C CS2(g) + 3Cl2(g) ® S2Cl2(g) + CCl4(g) given DH° = -231.1 kJ and DS° = -287.6 J/K. Select one: a. +56.5 kJ b. -316.9 kJ c. -518.7 kJ d. -56.5 kJ e. -145.3 kJ

e. -145.3 kJ

Calculate DS° for the following reaction, 2SO2(g) + O2(g) ® 2SO3(g) given S°[SO2(g)] = 248.2 J/mol×K, S°[O2(g)] = 205.1 J/mol×K, and S°[SO3(g)] = 256.8 J/mol×K. Select one: a. +187.9 J/K b. +196.5 J/K c. -94.0 J/K d. -196.5 J/K e. -187.9 J/K

e. -187.9 J/K

If a chemical reaction has a negative change in entropy, DS, then a. the reaction is spontaneous. b. the reaction is endothermic. c. the change in Gibbs free energy, DG, is negative. d. there is an increase in the order of the system. e. the equilibrium constant is greater than 1.

there is an increase in the order of the system.