What is ΔrG° at 500.0 K for the following reaction? Zn(s) + H2O(g) -> ZnO(s) + H2(g) Substance ΔfH°(kJ/mol-rxn) at 298 K S° (J/K·mol-rxn) at 298 K Zn(s) 0 41.6 H2O(g) –241.8 188.7 ZnO(s) –350.5 43.7 H2(g) 0 130.6   a. 80.7 kJ/mol-rxn b. –80.7 kJ/mol-rxn c. 92.0 kJ/mol-rxn d. –92.0 kJ/mol-rxn e. –136.7 kJ/mol-rxn

What is the pH of the solution which results from mixing 75 mL of 0.50 M NH3(aq) and 75 mL of 0.50 HCl(aq) at 25 °C? (Kb for NH3 = 1.8 x 10–5) a. 0.60 b. 2.67 c. 4.74 d. 4.93 e. 9.26

What is the pH of a 0.28 M solution of sodium propionate, NaC3H5O2, at 25°C? (propionic acid, HC3H5O2, is monoprotic and has a Ka = 1.3 x 10–5 at 25°C.) a. 6.26 b. 7.83 c. 8.10 d. 8.74 e. 9.17

Write a balanced half-reaction for the reduction of CrO42–(aq) to Cr(OH)3(s) in a basic solution. a. CrO42–(aq) + 3 OH–(aq) + 3 e– -> Cr(OH)3(s) + 2 O2(g) b. CrO42–(aq) + 3 H+(aq) + 3 e– -> Cr(OH)3(s) c. CrO42–(aq) + 3 H+(aq) -> Cr(OH)3(s) + 2 e– d. CrO42–(aq) + 4 H2O(l) + 3 e– -> Cr(OH)3(s) + 5 OH–(aq) e. CrO42–(aq) + 3 OH–(aq) -> Cr(OH)3(s) + 2 O2(g)

If 25 mL of 0.750 M HCl are added to 100. mL of 0.392 M NaOH, what is the final pH? a. 13.21 b. 2.79 c. 13.50 d. 1.50 e. 11.25

Estimate the boiling point of ethanol given the following thermodynamic parameters.       C2H5OH(l) C2H5OH(g)   ΔfH° (kJ/mol) –277.0 –235.3   S° (J/K×mol) 160.7 282.7   ΔfG° (kJ/mol) –174.7 –168.5   a. 290 °C b. 144 °C c. 51 °C d. 69 °C e. 342 °C

Simplify   . Assume the denominator is not equal zero.

Simplify   . Assume the denominator is not equal zero.

If 25 mL of 0.750 M HCl are added to 100. mL of 0.392 M NaOH, what is the final pH? a. 13.21 b. 2.79 c. 13.50 d. 1.50 e. 11.25

Consider the reaction A(aq) ⇌ 2 B(aq) where Kc = 4.1 at 25 °C. If 0.50 M A(aq) and 1.5 M B(aq) are initially present in a 1.0 L flask at 25 °C, what change in concentrations (if any) will occur in time? a. will decrease and will decrease. b. will decrease and will increase. c. will increase and will decrease. d. will increase and will increase. e. and remain unchanged.