1. Tardigrade
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  3. Chemistry
  4. The pKa of HCOOH is 3.8 and pKb of NH3 is 4.8, find the pH of aqueous solution of 1M HCOONH4.

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Q. The $pK_a$ of $HCOOH$ is $3.8$ and $pK_b$ of $NH_3$ is $4.8$, find the $pH$ of aqueous solution of $1M \,HCOONH_4$.

Equilibrium

Solution:

$HCOONH_4$ is a salt of weak acid and weak base;
$pH = \frac{1}{2} pK_w + \frac{1}{2} pK_a -\frac{1}{2} pK_b$
$\therefore pH = \frac{1}{2} \times 14 + \frac{1}{2} \times 3.8 - \frac{1}{2} \times 4.8$;
$pH = 6.5$