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Exam 2B
Spring 2006

Read all questions carefully. Numerical answers require units to obtain full credit. Answers without work shown will receive no credit. Remember to balance all chemical equations. The numerical answers to the pH questions are found from the following: 1.3, 1.30, 1.301, 4.6, 4.59, 4.590, 5.6, 5.59, 5.590, 9.7, 9.70, 9.701

Possibly useful information:

pH = –log[ H3O+ ]

 

pOH = –log[ OH ]

pH + pOH = 14.00 at 25 oC

 

 

Br2(l)Br2(g)

 

Kp = 0.28

Br2(g) + Cl2(g)2 BrCl(g)

 

Kp = 5.2


1. Complete and balance the following reactions:

a. solid calcium hydroxide plus aqueous hydroiodic acid

b. NH3(aq) + HN3(aq)

c. NaOH(aq) + H3PO4(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 Kc for the following reactions.

a. P4(s) + H2(g) PH3(g)

b. Cl2(g) + H2O(l) HOCl(aq) + HCl(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 nitric acid.

b. 2.5×10–5 M strontium hydroxide.

6. Consider the reaction shown below, which has H = –188.3 kJ/mol.

NH3(g) + HBr(g) NH4Br(s)

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

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

7. Estimate the equilibrium constant Kp for the following reaction to within 10% error.

Br2(l) + Cl2(g) BrCl(g)

8. Estimate the pH of a 0.010 M solution of arsenous acid, H3AsO3. Show all the steps needed to solve the problem until you are required to do algebra. Then make a chemically reasonable estimate of the pH. Ka = 6.6×10–10