Equilibrium Question 338
Question: If $ \alpha $ is the degree of ionization, $ C $ the concentration of a weak electrolyte and $ K_{a} $ the acid ionization constant, then the correct relationship between $ \alpha ,C $ and $ K_{a} $ is [CET Pune 1998; Pb. PMT 1998; RPMT 2002]
Options:
A) $ {{\alpha }^{2}}=\sqrt{\frac{K_{a}}{C}} $
B) $ {{\alpha }^{2}}=\sqrt{\frac{C}{K_{a}}} $
C) $ \alpha =\sqrt{\frac{K_{a}}{C}} $
D) $ \alpha =\sqrt{\frac{C}{K_{a}}} $
Show Answer
Answer:
Correct Answer: C
Solution:
According to the Ostwald-s dilution formula $ {{\alpha }^{2}}=\frac{K(1-\alpha )}{C} $ . But for weak electrolytes a is very small. So that $ (1-\alpha ) $ can be neglected. So that $ \alpha =\sqrt{\frac{K_{a}}{C}} $ .
