Exam 4B, Spring 2001

1. Complete and balance the following equations.

a. ammonia plus nitric acid

b. Cu²⁺(aq) + NH₃(aq) {NH₃ is in excess}

c. As₂O₃(s) + NO₃^–(aq) → H₃AsO₄(aq) + NO(g)

d. Bi(OH)₃(s) + Sn(OH)₃^–(aq) → Bi(s) + Sn(OH)₆^2–(aq)

2. Consider the reaction between solid calcium chloride and aqueous sodium sulfate.

a. Write the balanced reaction.

b. Find ΔH° for the reaction in units of kJ.

c. Find ΔS° for the reaction in units of J/K.

d. Find ΔG° for the reaction at 25 °C in units of kJ.

e. Find ΔG° for the reaction at 75 °C in units of kJ.

f. Is the reaction spontaneous or nonspontaneous at each temperature? Why?

3. Barium carbonate has a molar solubility of 5.7×10^–5 M at 25 °C and 6.1×10^–5 M at 85 °C. Find K_sp at each temperature and ΔH° and ΔS° for the solubilization reaction.

4. Consider the cell: Na(s) | Na⁺(aq) || Co²⁺(aq) | Co(s)

a. What is the balanced oxidation half-reaction?

b. What is the balanced reduction half-reaction?

c. What is the balanced net reaction?

d. What is the standard potential for the cell?

e. Is the reaction spontaneous or nonspontaneous? Why?

Answers