Chapter 18.2, Problem 14PP

Interpretation Introduction

Interpretation:

Expression of acidity constant is given. The balanced chemical equation is to be written.

Concept introduction:

Acid ionization constant tells about equilibrium that whether reactants are favored or products.

For a reaction,

$HA+H_{2}O\rightleftharpoons A^{-}+H_3{O}^{+}$

Acid ionization constant is given by:

$\begin{array}{l}{k}_a=\frac{\left[A^{-}\right]\times \left[H_3{O}^{+}\right]}{\left[HA\right]}\\ where,\\ \left[A^{-}\right]isconcentrationof{A}^{-}\\ \left[H_3{O}^{+}\right]isconcentrationof{H}_3{O}^{+}\\ \left[HA\right]isconcentrationofHA\end{array}$

Answer to Problem 14PP

The balanced equation is:

$HCN+H_{2}O\rightleftharpoons C{N}^{-}+H_3{O}^{+}$

Explanation of Solution

The acid ionization constant is:

$k_a=\frac{\left[C{N}^{-}\right]\times \left[H_3{O}^{+}\right]}{\left[HCN\right]}$

Therefore, comparing with standard formula the equation is:

$HCN+H_{2}O\rightleftharpoons C{N}^{-}+H_3{O}^{+}$

Conclusion

Thus, the equation for the given expression is:

$HCN+H_{2}O\rightleftharpoons C{N}^{-}+H_3{O}^{+}$