1. at 25 C a saturated solution of a metal hydroxide, M (OH)2, has a pH of 9.0.

Question

1. at 25 C a saturated solution of a metal hydroxide, M (OH)2, has a pH of 9.0. What is the value of the solubility product constant, Ksp, Of M(OH)2 (s) at 25 C?

a) 5.0*10-28

b) 1.0*10-27

c) 5.0*10-19

d) 5.0*10-16

e) 1.0*10-15

2. In the titration of a weak monoprotic acid with a strong base, the pH at the endpoint will be

A) equal to the pKa of the weak acid.

b) less than 7.00.
c) greater than 7.00.

d) less than the pKa of the weak acid.

e) equal to 7.00.

3. Which of the following mixtures will be a buffer when dissolved in 1 L of water?

A) 0.3 mol KCl and 0.3 mol HCl

B) 0.2 mol HC2H3O2 and 0.1 mol NaOH

C) 0.4 mol NH3 and 0.4 mol

D) 0.1 mol Ba(OH)2 and 0.2 HCl mol HCl

E) 0.2 mol HBr and 0.1 mol NaOH

Explanation / Answer

1. pH + pOH = 14 if pH is 9.0 then pOH becomes as follows.

pOH = 5.0
[OH-] = 10^-pOH = 1.0*10^-5 M
[M2+] = (1.0*10^-5)/2 = 5*10^-6 M

M(OH)2 <----> M^+2 + 2 OH-
Ksp = (( 5*10^-6) ( 1.0 *10^-5)^2)

      = 5.0*10^-16

2. In the titration of a weak monoprotic acid with a strong base, the pH at the endpoint will be

c) greater than 7.00

3. Which of the following mixtures will be a buffer when dissolved in 1 L of water?

Buffer is a mixture of weak acid/weak base and its salt with strong base/strong acid.

B) 0.2 mol HC2H3O2 and 0.1 mol NaOH

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