Calculate the ratio of sodium formate and formic acid Ka - 2-10-4 in a buffer solution of pH - 4-3-

pK_a= logK_a= log 2 × 10^ 4=3.698 For acidic buffer solution, pH=pK_a + log [HCOONa]/[HCOOH] Substitute values in the above expression. 4.3=3.698+l ...

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Standard XII

Chemistry

Basic Buffer Action

Calculate the...

Question

Calculate the ratio of sodium formate and formic acid $(K_{a} = 2 \times 10^{- 4})$ in a buffer solution of $p H = 4.3$ .

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Solution

$p K_{a} = - l o g K_{a} = - l o g 2 \times 10^{- 4} = 3.698$
For acidic buffer solution,
$p H = p K_{a} + l o g \frac{[H C O O N a]}{[H C O O H]}$
Substitute values in the above expression.
$4.3 = 3.698 + l o g \frac{[H C O O N a]}{[H C O O H]}$
$l o g \frac{[H C O O N a]}{[H C O O H]} = 0.601$
$\frac{[H C O O N a]}{[H C O O H]} = 3.99 = 4$
Hence, the ratio of sodium formate to formic acid is $4 : 1$ .

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Calculate the ratio of sodium formate and formic acid (Ka=2×10−4) in a buffer solution of pH=4.3.

pKa=−logKa=−log2×10−4=3.698For acidic buffer solution,pH=pKa+log[HCOONa][HCOOH]Substitute values in the above expression.4.3=3.698+log[HCOONa][HCOOH]log[HCOONa][HCOOH]=0.601[HCOONa][HCOOH]=3.99=4Hence, the ratio of sodium formate to formic acid is 4:1.

Calculate the ratio of sodium formate and formic acid $(K_{a} = 2 \times 10^{- 4})$ in a buffer solution of $p H = 4.3$ .