Question

Chem II Common Assignment: Equilibrium and Buffers

1. Calculate the equilibrium concentrations of all species present and the pH of a solution obtained by adding 0.100 moles of solid NaOH to 1.00 L of 15.0 M NH3. Kb = 1.8 × 10–5

2. One mole of a weak acid HA was dissolved in 2.0 L of water. After the system had come to equilibrium, the concentration of HA was found to be 0.45 M. Calculate the Ka for this weak acid.

3. Calculate the pH of a solution formed by mixing 50.0 mL of 0.40 M NH3 solution with 50.0 mL of a 0.40 M HCl solution. Is the resulting solution acidic, basic, or neutral? Ka = 5.6 × 10–10

4. Which of the following mixtures would result in buffered solutions when 1.0 L of each of the two solutions is combined? Circle the letter of the appropriate response(s).

a. 1.0 M HBr and 1.0 M NaBr

d. 1.0 M NH3 and 1.0 M NH4 Cl

b. 2.0 M HF and 1.0 M NaOH

e. 1.0 M NH3 and 0.50 M HCl

c. 1.0 M HF and 1.0 M NaOH

f. 1.0 M HNO3 and 0.50 M NaOH

5. How many grams of solid NaOH must be added to 1.00 L of 2.0 M CH3COOH (acetic acid) to produce a solution that is buffered at each pH? Ka = 1.76 × 10–5

a. pH = pKa

b. pH = 4.00

Answer 1

1.