$$K_a$$ for butyric acid ($$C_3H_7COOH$$) is $$2 \times 10^{-5}$$. The pH of 0.2 M solution of butyric acid is _____ $$\times 10^{-1}$$. (Nearest integer) [Given $$\log 2 = 0.30$$]

We are given that the acid dissociation constant $$K_a$$ for butyric acid ($$C_3H_7COOH$$) is $$2 \times 10^{-5}$$, the concentration $$C$$ is $$0.2$$ M, and $$\log 2 = 0.30$$.

Since butyric acid is a weak acid, the hydrogen ion concentration can be determined using the relation $$[H^+] = \sqrt{K_a \times C}$$. Substituting the known values into this expression yields $$[H^+] = \sqrt{2 \times 10^{-5} \times 0.2} = \sqrt{4 \times 10^{-6}} = 2 \times 10^{-3} \text{ M}$$.

From the above hydrogen ion concentration, we calculate the pH as follows: $$pH = -\log[H^+] = -\log(2 \times 10^{-3}) = -[\log 2 + \log 10^{-3}] = -[0.30 + (-3)] = -[0.30 - 3] = -(-2.70) = 2.70$$.

Expressing this pH in the required form gives $$pH = 2.70 = 27 \times 10^{-1}$$. Therefore, the value is 27.