A buffer is 0.10 M in CH3COOH and 0.10 M in CH3COONa (pK_a = 4.74). Select the correct statement(s).

Adding 0.010 mol HCl to 1.00 L of it lowers the pH to about 4.65

Its pH is (ideally) unchanged on two-fold dilution

Adding 0.010 mol HCl to 1.00 L of it lowers the pH to about 4.65

Its pH is (ideally) unchanged on two-fold dilution

Its buffer capacity is greatest when [CH3COO-]/[CH3COOH] = 10

JEE Main levelOne or more correct optionsDifficulty 2 of 3ia194

A buffer is $0.10 M$ in $CH X_{3} COOH$ and $0.10 M$ in $CH X_{3} COONa$ ( $p K_{a} = 4.74$ ). Select the correct statement(s).

AAdding $0.010 mol$ $HCl$ to $1.00 L$ of it lowers the pH to about $4.65$
BIts pH is (ideally) unchanged on two-fold dilution
CIts buffer capacity is greatest when $[CH X_{3} COO X^{-}] / [CH X_{3} COOH] = 10$
DIts pH is $4.74$

pH = p K_{a} + lo g 1 = 4.74

, and dilution leaves the ratio unchanged. After

0.010 mol

HCl

: acid

0.11

, base

0.09

, so

pH = 4.74 + lo g (0.09/0.11) = 4.65

. Capacity is greatest at a ratio of

1

, not

10