Exam 2A, Spring 2006

1. Complete and balance the following reactions:

a. solid calcium hydroxide plus aqueous hydrobromic acid

b. NH₃(aq) + HN₃(aq)

c. KOH(aq) + H₂SO₄(aq)

2. Complete and balance the following reaction and identify the acid, the base, the conjugate acid, and the conjugate base:

bicarbonate ion + hydroxide ion

3. Write the mass action expression for K_c for the following reactions.

a. N₂(g) + H₂(g) → ← NH₃(g)

b. Br₂(l) + H₂O(l) → ← HOBr(aq) + HBr(aq)

4. Consider bicarbonate ion and hydrogen phosphate ion. Draw the Lewis dot structure for each species and identify the stronger acid in the pair. Briefly (5 words or less) justify your reasoning.

5. Write the reaction that occurs in water and calculate the pH and pOH of the following solutions:

a. 5.0×10^–2 M perchloric acid.

b. 2.5×10^–5 M magnesium hydroxide.

6. Consider the reaction shown below, which has ΔH = –176.0 kJ/mol.

NH₃(g) + HCl(g) → ← NH₄Cl(s)

a. Which way will the reaction shift if ammonium chloride is added to the reaction? Explain.

b. Which way will the reaction shift if the temperature is raised? Explain.

7. Estimate the equilibrium constant K_p for the following reaction.

Br₂(l) + Cl₂(g) → ← BrCl(g)

The following data has been reported:

Br₂(l) → ← Br₂(g) K_p = 0.28

Br₂(g) + Cl₂(g) → ← BrCl(g) K_p = 5.2

8. Estimate the pH of a 1.0 M solution of arsenous acid, H₃AsO₃. K_a = 6.6×10^–10

Answers