(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.