1. Benedict test. Benedict reagent is a mixture of sodium carbonate and sodium citrate. This on reaction with aldehyde gives red precipitate of Cu2S.
2. Acidic strength is related to the stability of carboxylate anion.
Acid of each pair is stronger:
(i) CH2FCOOH. This is due to the high electron with drawing effect of F.
This is due to the high electron with drawing effect of the -CF3 group.