A buffer is made with [CH3COOH] = 0.10 M and [CH3COO-] = 0.20 M (pK_a = 4.74, log 2 = 0.301). Select the correct statements.

After 10-fold dilution with water its pH, by the Henderson equation, is still 5.04

JEE Main levelOne or more correct optionsDifficulty 2 of 3ie143

A buffer is made with $[CH X_{3} COOH] = 0.10 M$ and $[CH X_{3} COO X^{-}] = 0.20 M$ ( $p K_{a} = 4.74$ , $lo g 2 = 0.301$ ). Select the correct statements.

AIts pH is 5.04
BIts pH is 4.44
CIts pH equals $p K_{a}$
DAfter 10-fold dilution with water its pH, by the Henderson equation, is still 5.04

pH =

4.74 + lo g (0.20/0.10) = 5.04

. So (a) is correct, (b) and (c) are wrong. On dilution the ratio

[A X^{-}] / [HA]

is unchanged, so by the Henderson equation the pH is still 5.04 and (d) is correct.