Name________________________

Solve the following problem related to the solubility equilibrium in an aqueous solution. The solubility of Cu(OH)₂ is 1.72x10^-6 gram per 100.0 mL of solution at 25°c.

1. Write the balanced chemical equation for the dissociation of Cu(OH)2 in aqueous solution.

2. Calculate the solubility (in moles per liter) of Cu(OH)₂ at 25°c

3. Calculate the value of the solubility-product constant, Ksp for Cu(OH)₂ at 25°c

Problems (4-6)

At 25°C Ksp for PbCl_2(s) is 1.6 x 10^-5 and Ksp for AgCl is 1.8 x 10^-10

4. If 60mL of 0.0400M NaCl is added to 60.0mL of 0.300M Pb(NO₃)₂, will a precipitate form? Assume that volumes are additive. Show calculations to support your answer.

5. Calculate the equilibrium concentration of Pb⁺² in 1.00L of saturated PbCl₂solution to which 0.250 mole of NaCl has been added. Assume no volume change occurs.

6. If 0.100 M NaCl is added slowly to a beaker containing both 0.120 M AgNO₃ and 0.150M Pb(NO₃)₂ at 25°C, which will precipitate first, AgCl or PbCl₂? Show calculations to support your answer.

7. How many grams of solid NaOH must be added to 75.0mL of 0.25M HOCl to obtain a buffer solution that has a pH of 8.25? Assume the addition of the solid NaOH results in a negligible change in volume. Ka = 3.5x10^-8

8. 25.0mL of barium hydroxide is titrated to the equivalence point with 36.5mL of 0.15M phosphoric acid. What is the molarity of the barium hydroxide.

 Answers

(2) 1.76 x 10^-7 M (3) 3.6 x 10^-20 (don't forget about the OH^- in the water!!!)

(4) Q = 6x10^-5 Q>Ksp yes ppt forms (5) 2.56x10^-4

(6) AgCl will ppt first. AgCl, Q = 0.012 >>>>>>>> Ksp

PbCl₂, Q = 0.0015 >>> Ksp

(7) 0.646g NaOH (8) 0.329M