1. A 1. 00 L solution is prepared by placing 0
A 1.00 L solution is prepared by placing 0.10 moles of a weak acid (HA) and moles of its conjugate base NaA. Determine the pH of the solution. The Ka of the HA is 1.4 x
Chemistry:
HA + H2O ↔ H3O A- I. C. E.
-x x x
0.10-x x x
Try dropping the +x and the –x terms (5 % rule).
X = [H3O+] = 2.8 x 10-5
pH = -log[x] = 4.55

2. A solution is 0. 095 M in ascorbic acid and 0
A solution is M in ascorbic acid and M in sodium hydrogen ascorbate. Determine the pH of the solution. Ka1 of the H2C6H6O6 is 6.8 x 10-5, Ka2 = 2.8 x
Chemistry:
H2C6H6O H2O ↔ H3O HC6H6O6- I. C. E.
-x x x
0.095-x x x
Try dropping the +x and the –x terms (5 % rule).
X = [H3O+] = 1.17 x 10-4
pH = -log[x] = 3.95

3. A 1. 00 L solution is prepared by placing 0
A 1.00 L solution is prepared by placing 0.10 moles of a weak base (B) and moles of its conjugate acid BHCl. Determine the pH of the solution. The Kb of the B is 1.4 x
Chemistry:
B + H2O ↔ OH BH+ I. C. E.
-x x x
0.10-x x x
Try dropping the +x and the –x terms (5 % rule).
X = [OH-] = 2.8 x 10-5
pOH = -log[x] = and pH = 9.45

4. A solution is prepared that has a trimethlyamine, (CH3)3N, concentration of M and a concentration of (CH3)3NHCl of M. Determine the pH of the solution. The Kb of trimethylamine =6.4 x 10-5.
Chemistry:
(CH3)3N + H2O ↔ (CH3)3NH OH- I. C. E.
-x x x
0.100-x x x
Try dropping the +x and the –x terms (5 % rule).
X = [OH-] = 1.28 x 10-5
pOH = -log[x] = and pH = 10.11

5. Determine the Ka of a 0.10 M acid solution that has a pH of 3.45.
Chemistry
HA + H2O ↔ H3O+ + A- NA I. C. E.
-x x x
0.10 – x x x
Since x = [H3O+] and pH = 3.45; [H3O+] = 10-pH = x 10-4