Exam 2B, Spring 2003

1. Complete and balance the following acid/base reactions.

a. aqueous sulfuric acid plus solid magnesium hydroxide

b. aqueous hydroiodic acid plus water

c. HClO₂(aq) + CO₃^2–(aq)

d. HN₃(aq) + H₂O(l)

2. Write the chemical reaction needed to determine the pH and give the pH for the following solutions.

a. 0.010 M perchloric acid.

b. 0.0010 M barium hydroxide

3. Indicate the stronger acid in each pair. Explain your reasoning in 5 words or less. For the stronger acid, write out the balanced reaction of the acid with water. label the conjugate acid/base pairs for each reaction

a. CCl₃COOH vs. CH₃COOH

b. H₂SO₄ vs. HNO₃

c. HCrO₄^– vs. HMnO₄

4. Pyrophosphoric acid is polyprotic, H₄P₂O₇, with K_a1 = 3.0×10^–2, K_a2 = 4.4×10^–3, K_a3 = 2.5×10^–7, and K_a4 = 5.6×10^–10. Although it is a weak acid, a 0.010 M solution is greater than 100 % ionized and has a pH of about 1.9. Explain how this can happen, using chemical reactions to supplement your argument.

5. A 0.10 M solution of hydrogen selenate ion (HSeO₄^–, K_a = 2.2×10^–2) was prepared. Find the pH.

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