QUESTION 12 Determine the pH of a 0.22 M NaF solution at 25°C. The K a of HF is

Question

QUESTION 12

       Determine the pH of a 0.22 M NaF solution at 25°C. The Ka of HF is 3.5 × 10-5.

QUESTION 13

       Determine the pH of a 0.227 M C5H5N solution at 25°C. The Kb of C5H5N is 1.7 × 10-9.

QUESTION 14

       Determine the pH of a 0.461 M C6H5CO2H M solution if the Ka of C6H5CO2H is 6.5 x 10-5.

5 points

QUESTION 15

       Determine the value of Kc for the following reaction if the equilibrium concentrations are as follows: [N2]eq = 3.6 M, [O2]eq = 4.1 M, [N2O]eq = 3.3 × 10-18 M.

         2 N2(g) + O2(g) 2 N2O(g)

Explanation / Answer

12. Na+(aq) + F-(aq) + H2O(l) -------> NaOH(aq) + HF(aq)

A strong base and a weak acid.
Ka + Kb = 1x10-14 ;

Kb = 1x10-14 / 3.5x 10-5 = 2.86 x10-10
Kb = [Na+][OH-] / [NaF]
Kb = x * x / 0.22

2.86 x10-10= * x / 0.22
x = 7.93 * 10-6 = [OH-]
pOH = -log[OH-]

       = 5.101

pH = 14-5.101 = 8.899

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