Chapter 18, Problem 102A

Interpretation Introduction

Interpretation:

The chemical equation is to be written when a base is added to $H_{2}P{O}_4{}^{-}/HP{O}_4{}^{2-}$ buffer system.

Concept introduction:

Buffer solution is a solution in which there is no change in $pH$ takes place on adding small amount of acid and base.

Answer to Problem 102A

$O{H}^{-}+H_{2}P{O}_4{}^{-}\to H_{2}O+HP{O}_4{}^{2-}$

Explanation of Solution

When base is added to $H_{2}P{O}_4{}^{-}/HP{O}_4{}^{2-}$ buffer system, it reacts with $H_{2}P{O}_4{}^{-}$ to nullify the effect of addition of the base.

The equation is given as:

$O{H}^{-}+H_{2}P{O}_4{}^{-}\to H_{2}O+HP{O}_4{}^{2-}$

Conclusion

Thus buffer system resists the change in the value of $pH$ on adding small amount of acid and base.