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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) + CO32(aq)

d. HN3(aq) + H2O(l)


2. Write the chemical reaction needed to determine the pH and give the pH for the following solutions. Possible answers are: 2, 2.0, 2.00, 2.000, 2.699, 2.7, 2.70, 3, 3.0, 3.00, 3.000, 11, 11.0, 11.00, 11.000, 11.3, 11.30, 11.301, 12, 12.0, 12.00, 12.000.

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 Ka1 = 3.0×10–2, Ka2 = 4.4×10–3, Ka3 = 2.5×10–7, and Ka4 = 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, Ka = 2.2×102) was prepared. Find the pH. Set the problem up and stop when you reach the stage to do algebra. Select the pH from one of the following: 1.43, 2.13, 3.02, 10.98, 11.87, or 12.57. No work = no credit.