AP Chemistry Chapter 19 Thermodynamics Practice Test

AP Chemistry Chapter 19 Thermodynamics Practice TestMultiple ChoiceIdentify the choice that best completes the statement or answers the question.____1.G refers to the free-energy change associated with which of the following?

a.the formation of 1 mol of a compound from its constituent elements.

b.the decomposition of 1 mole of a compound into its constituent elements.

c.the freezing of 1 mol of a substance.

d.the melting of 1 mol of a substance.

e.all of the above.

____2.Under what conditions can we absolutely say a system is at equilibrium at constant pressure and temperature?

a.H = 0d.G > 0

b.H > 0e.S > 0

c.G = 0

____3.Which of the following substances would you expect to have the highest entropy at 1 atm of pressure?

a.HO(s)(1 mol)d.0.5 mol of ethanol in 0.5 mol of HO(l)

b.HO(l)(1 mol)e.a gaseous solution of 0.5 mol of HO(g) and 0.5 mol of CH(g)

c.HO(g)(1 mol)

____4.For any isolated spontaneous process that is endothermic, which of the following conditions are true:

(1) G< 0 (2) G> 0 (3) S< 0 (4)S> 0 (5) S< 0 (6) S> 0

a.(1, (3) and (4)d.(1), (4) and (6)

b.(2), (4) and (6)e.(2), (4) and (6)

c.(1), (4) and (5)

____5.For which of the following changes would you expect S to be less than zero?

a.HO(l) HO(g)d.CO(s) CO(g)

b.CO(g) + O(g) CO(g)e.2 AgCl(s) 2 Ag(s) + Cl(g)

c.2 SO(g) 2 SO(g) + O(g)

____6.When KNO dissolves in water at room temperature, H is positive for the dissolution process. Given this information, what can you conclude?

a.G > 0 for the dissolution process.d.S > 0 for the dissolution process.

b.G = 0 for the dissolution process.e.S < 0 for the dissolution process.

c.The dissolving of salts in water is always a spontaneous process.

____7.Which of the following is true for the sublimation of solid CO at room temperature and pressure?

a.H and S are positive.d.G becomes more positive as temperature increases.

b.H and S are negative.e.G is positive.

c.H is negative and S are positive.

____8.Which of the following can be used to calculate directly the value of an equilibrium constant for a reaction at a given temperature?

a.Hd.G

b.He.G

c.S

____9.Calculate G for the following reaction at 25C

4 NO(g) + 6 HO(g) 5 O(g) + 4 NH(g)

given the following G values: NO, 86.71 kJ/mol; HO, 228.61 kJ/mol; O, 0.0 kJ/mol; NH, 16.66 kJ/mol.

a.958.2 kJd.1318.18 kJ

b.2145.14 kJe.1318.18 kJ

c.2145.14 kJ

____10.Estimate the normal boiling point for HCl, given the following information:

H= 16.13 kJ/mol and S= 85.77 J/molK

a.188Cd.0.189 K

b.188 Ke.100C

c.0.189C

____11.The standard free energy of formation, G, for sodium chloride is the free energy change for which of the following reactions?

a.Na(g) + Cl(g) NaCl(g)d.Na(s) + Cl(g) NaCl(s)

b.Na(g) + Cl(g) NaCl(s)e.2 NaCl(s) 2Na(s) + Cl(g)

c.2 Na(s) + Cl(g) 2 NaCl(s)

____12.For which of these processes is the value of S expected to be negative?

I. NaCl is dissolved in water.

II. Steam condenses to liquid water.

III. MgCO is decomposed into MgO and CO.

a.I onlyd.II and III only

b.I and III onlye.I and II only

c.II only

____13.What are the signs of the enthalpy change and entropy change for the melting of ice?

HO(s) HO(l)

The signs represent H and S, respectively.

a.+, +d.,

b., e.0, 0

c.,

____14.Under which set of conditions does a temperature exist at which equilibrium can be established with all reactants and products in standard states?I. S is +, H is +

II. S is , H is

III. S is +, H is

a.I onlyd.I and II only

b.II onlye.I and III only

c.III only

____15.Which of the following substances is expected to have the largest standard molar entropy?

a.HO(s)d.HO(l)

b.HO(l)e.HO(g)

c.HO(g)

____16.In which process would G be expected to be positive?

a.melting ice at 10C and 1.0 atm pressured.sublimation of dry ice at 25C

b.water evaporating at 25C into dry aire.a burning campfire

c.cooling hot water to room temperature

____17.Which is not expected to have a value of zero?

a.H for O(g)d.H for Br(l)

b.G for K(g)e.G for O(g)

c.S for Ca(s) at 0 K

____18.Which process is exothermic and occurs with a decrease in entropy?

a.HO(l) HO(s)d.2 HO(l) 2 H(g) + O(g)

b.HO(s) HO(l)e.HO(l) HO(g)

c.HO(s) HO(g)

____19.In order to calculate the entropy change for the following reaction at 25C and one atmosphere, what additional thermodynamic information is needed? C(s, graphite) + O2(g) CO2(g) a.H for CO(g)

b.G for CO(g)

c.H and G for CO(g)

d.S for CO(g)

e.H and G for both C(s, graphite) and O(g)

____20.For a certain reaction, H = 150 kJ/mol and S = 50 J/mol K. Which of the following statements is true about the reaction?

a.It is spontaneous at high temperatures only.

b.It is spontaneous at low temperatures only.

c.It is spontaneous at all temperatures.

d.It is nonspontaneous at all temperatures.

e.There is no temperature at which the reaction will reach equilibrium.

Problem

21.Calculate the pH of water at 40C given the following information for the equilibrium at 25C:

HO(l) H(aq) + OH(aq)

G(kJ/mol)

237.2 0 157.3

H(kJ/mol)

285.8 0 230.0

(Hint: Determine G and K at 40C to solve for pH.)