Question

If $C$ the concentration of a weak electrolyte, $\alpha $ is the degree of ionization and $K_{a}$ is the acid ionization constant, then the correct relationship between $\alpha ,C$ and $K_{a}$ is

• A. $\alpha ^{2}=\sqrt{\frac{K_{a}}{C}}$
• B. $\alpha ^{2}=\sqrt{\frac{C}{K_{a}}}$
• C. $\alpha =\sqrt{\frac{C}{K_{a}}}$
• D. $\alpha =\sqrt{\frac{K_{a}}{C}}$

Answer 1

Answer: (D)

According to the Ostwald’s dilution formula $\left(\alpha \right)^{2}=\frac{K \left(\right. 1 - \alpha \left.\right)}{C}$ . But for weak electrolytes α is very small. So that $\left(\right.1-\alpha \left.\right)$ can be neglected. So that $\alpha =\sqrt{\frac{K_{a}}{C}}$ .