What will be the $p H$ of an aqueous solution of $1.0 M$ ammonium formate?
Given: $p K_{a} = 3.8$ and $p K_{b} = 4.8$ .

7.5

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3.4

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6.5

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10.2

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Solution

The correct option is C $6.5$
Ammonium formate is a salt of weak acid formic acid and weak base ammonia.

The expression for the pH of ammonium formate is $p H = 0.5 (p K_{w} + p K_{a} - p K_{b})$ .

Substitute values in the above expression.
$p H = 0.5 (14 + 3.8 - 4.8) = 6.5$

Option C is correct.

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Similar questions

1.0 M

p K_{a}

= 3.8

p K_{b}

= 4.8

1 M

(p K_{a} = 3.8, p K_{b} = 4.8)

p H

0.1 M

25^{o} C

Given : p K_{a} (H C O O H) = 3.8 a n d p K_{b} (N H_{4} O H) = 4.8

H C O O N H_{4}

p K_{a} (H C O O H) = 3.8 a n d p K_{b} = 4.8

0.1 M

(p K_{a} = 9.04, p K_{b} = 4.73)

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