The ionisation constants of formic acid and ammonium hydroxide are 2- 10-4 and 2- 10-5respectively- The pH of aqueous solution of ammonium formate is -

The correct option is B 6.5For a salt of weak acid and weak base, #160; [H]^+= √(K_w × K_a)/√(K_b) .Substitute values in the above expression, we get ...

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Standard XII

Chemistry

Salt of Weak Acid and Weak Base

The ionisatio...

Question

The ionisation constants of formic acid and ammonium hydroxide are $2 \times 10^{- 4}$ and $2 \times 10^{- 5}$ respectively. The pH of aqueous solution of ammonium formate is :

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Solution

The correct option is B 6.5
For a salt of weak acid and weak base, $[H]^{+} = \frac{\sqrt{K_{w} \times K_{a}}}{\sqrt{K_{b}}}$ .
Substitute values in the above expression, we get
$[H]^{+} = \frac{\sqrt{1 \times 10^{- 14} \times 2 \times 10^{- 4}}}{\sqrt{2 \times 10^{- 5}}} = 3.16 \times 10^{- 7}$ .
$p H = - l o g [H]^{+} = - l o g (3.16 \times 10^{- 7}) = 6.5$ .

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Similar questions

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The ionisation constants of formic acid and ammonium hydroxide are 2×10−4 and 2×10−5respectively. The pH of aqueous solution of ammonium formate is :

The correct option is B 6.5For a salt of weak acid and weak base, [H]+=√Kw×Ka√Kb.Substitute values in the above expression, we get[H]+=√1×10−14×2×10−4√2×10−5=3.16×10−7.pH=−log[H]+=−log(3.16×10−7)=6.5.

The ionisation constants of formic acid and ammonium hydroxide are $2 \times 10^{- 4}$ and $2 \times 10^{- 5}$ respectively. The pH of aqueous solution of ammonium formate is :