Please I Need Help With the Chemistry Aqueous Equilibria problem?

Question

1(a) Write a balanced equation and corresponding solubility product expression for solid zinc hydroxide,Zn(OH)2, in equilibrium with its ions in solution. 

(b) This solution has a pH of 8.87. Determine the Ksp of Zn(OH)2. 

2(a) Write a balanced equation and corresponding solubility product expression for barium chromate, BaCrO4, in equilibrium with its ions in solution. (Ksp= 1.2 x 10^-11) 

(b) Determine the concentration of Ba^2+in a saturated solution of BaCrO4. 

(c) Suppose BaCrO4 is added to a solution that contains 0.20 M CrO4^2-. Determine the concentration of Ba^2+when equilibrium is achieved.

Answer 1

a) Zn(OH)₂(s) <===> Zn²⁺(aq) + 2OH^-(aq)

Ksp = [Zn²⁺][OH^-]²

b) From pH = 8.87, determine pOH; pOH = 14 - 8.87 = 5.13; Thus [OH-] = 1x10^-5.13 = 7.41x10^-6

Since [Zn^2+] is 1/2 that of OH-, [Zn^2+] = 3.71x10^-6

Ksp = [Zn^2+][OH-]² = (3.7x10^-6)(7.41x10^-6)² = 2.03x10^-16

For BaCrO4 follow same procedure as above.

Ksp expression is Ksp = [Ba²⁺][CrO₄^2-]

Plug in x for each ion and solve for x which will be [Ba²⁺]

For the final part, use the Ksp expression and plug in 0.2 M for CrO₄^2- and solve again for Ba²⁺