Answer
(a) and (b) are buffers, because they have a conjugate weak acid-base in an adequate ratio.
Work Step by Step
1. Identify acid-base conjugate pairs:
(a) $CH_3CH_2COOH$ and $CH_3CH_2COO^-$
(b) $HOCl$ and $OCl^-$
(c) No conjugate pairs.
(d) No conjugate pairs.
2. Analyze and compare their concentrations:
(a) 1.0M and 0.20M : Acceptable*.
(b) 0.10M and 0.10M: Acceptable*.
- Ratio between 0.1 and 10.
** If there is any reaction, you should simulate it and analyze the results. But, in this case, the compounds in (c) and (d) don't react.