Question

In: Chemistry

16. A solution is made by adding 0.500 mols of NaF and 0.500 mols of KCN...

16. A solution is made by adding 0.500 mols of NaF and 0.500 mols of KCN to 0.75L of water. What will the pH of this solution be? You may need to refer to the Ka/Kb table attached to this exam for this problem. Give your answer to two decimal places.

Expert Solution

F- + H2O -----------------> HF + OH-

0.5 0 0

0.5-x x x

Kb = x^2 / 0.5-x

1.59 x 10^-11 = x^2 / 0.5-x

x = 2.82 x 10^-6

[OH-] = 2.82 x 10^-6 M

CN- + H2O ------------------> HCN + OH-

0.5 0 0

0.5 -x x x

Kb = x^2 / 0.5-x

1.59 x 10^-5 = x^2 / 0.5 - x

x = 2.81 x 10^-3

[OH-] = 2.81 x 10^-3 M

total [OH-] = 2.82 x 10^-6 + 2.81 x 10^-3

= 2.81 x 10^-3 M

pOH = 2.55

pH = 11.45

queen_honey_blossom answered 2 years ago

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