How do you find the pH/molarity/Conjugate Acid-base of the following solutions?

Question

1. 5.0 x 10^-5 M solution of Ba(OH)2 is prepared. What is the pH of the solution?

2. In a titration, 25.9 mL of 3.4 x10^-3 M Ba(OH)2 neutralized 16.6 mL of HCL solution. What is the molarity of the HCL solution?

3. Identify the conjuage acid-base pairs for the following reaction:

CH3NH2(aq) + Ch3COOH(aq) <---> Ch3NH3^+(Aq) + CH3COO^- (aq)

Answer 1

Ba(OH)2 &gt;&gt; Ba2+ + 2 OH-

[OH-] = 2 x 5.0 x 10^-5 = 1.0 x 10^-4 M

pOH = - log 1.0 x 10^-4 = 4.0

pH = 14 - pOH = 14 - 4.0 = 10.&#039;

Moles Ba(OH)2 = 0.0259 L x 3.4 x 10^-3 = 8.81 x 10^-5

Moles OH- = 2 x 8.81 x 10^-5 = 1.76 x 10^-4 = moles HCl

M of HCl = 1.76 x 10^-4 mol / 0.0166 L = 0.0106 M

CH3NH2 = base and CH3NH3+ is its conjugate acid

CH3COOH = acid and CH3COO- is its conjugate base