Final Exam B, Spring 2018

1. Complete and balance the following in aqueous solutin:

a. nitrite ion plus nitric acid

b. calcium hydroxide plus hydrobromic acid

c. H₃PO₄(aq) + Cr(C₂H₃O₂)₃(aq)

d. Ti³⁺(aq) + H₂O(l)

e. thiocyanate ion plus water

f. K₂S(aq) + Fe(NO₃)₃(aq)

g. dichromate ion plus chlorite ion giving chromium 3+ ion and perchloric acid

h. MnO₄^2–(aq) + C₂O₄^2–(aq) → Mn(OH)₂(s) + CO₂(g)

2. The data given below was found for the reaction

[Cr(NH₃)₅(H₂O)]³⁺(aq) + Br^–(aq) → [Cr(NH₃)₅Br]²⁺(aq) + H₂O(l)

[[Cr(NH₃)₅(H₂O)]³⁺] (M) [Br^–] (M)Initial Rate (M·s^–1)

0.00100.00103.7×10^–2

0.00200.00107.4×10^–2

0.00200.00201.5×10^–1

Find the rate law and the rate constant (including units).

3. Find the pH of a 0.10 M solution of benzoic acid (C₆H₅CO₂H).

4. Find the molar solubility of PbI₂ in water.

5. Consider the reaction between Pb(OH)₂(s) and HCl(g) at 25 °C.

a. Find ΔG° for the solubilization of Pb(OH)₂.

b. Find ΔG° for the autoionization of water.

c. Find ΔG° for the solubilization of PbCl₂.

d. Find ΔG° for the reaction of HCl(g) with water.

e. Find ΔG° for the reaction of Pb(OH)₂(s) with HCl(g).

6. Consider the reaction OF₂(g) + Cl^–(aq) → Cl₂(g) + H₂O(l) + F^–(aq)

a. Find the oxidation numbers in all of the atoms in the following reactants and products.

Cl in Cl₂

H in H₂O

O in H₂O

O in OF₂

F in OF₂

F in F^–

b. Balance the reaction under acidic conditions.

c. Find the standard potential for the reaction.

d. Find ΔG° for the reaction.

e. Is the reaction spontaneous or nonspontaneous? Why?

7. Consider the cell:

Pt(s) | PbSO₄(s) | PbO₂(s) | SO₄^2–(aq) | pH = 0 || PbO₂(s) | Pb²⁺(aq) | pH = 0 | Pt(s)

a. Write the oxidation half-reaction.

b. Write the reduction half-reaction.

c. Write the net reaction.

d. Find the standard potential at 25 °C.

e. Find the equilibrium constant for the reaction.

f. What is the appropriate label (K_a, K_b, etc.) for the equilibrium constant?

Answers