Arrange the following compounds in increasing order of their property as indicated: (i) F-CH₂COOH, O₂N-CH₂COOH, CH₃COOH, HCOOH - acid character (ii) Acetone, Acetaldehyde, Benzaldehyde, Acetophenone - reactivity towards addition of HCN

(i) The order of electron withdrawing ability is -NO₂ > F > -H > -CH₃. Therefore, the order of acidic character is - O₂N-CH₂COOH > F-CH₂COOH > HCOOH > CH₃COOH.
(ii) Addition of HCN is a nucleophilic addition reaction. The +I effect is more in ketone than in aldehyde. Thus ketone will be least reactive in nucleophilic addition reactions. The presence of electron withdrawing group increases the reactivity towards the addition of HCN while the presence of electron donating group decreases the reactivity of compound towards nucleophilic addition reaction. Benzaldehyde does not favour nucleophilic addition reaction due to resonance stabilisation. Hence the increasing order of reactivity towards the addition of HCN will be - Acetophenone < Benzaldehyde < Acetone < Acetaldehyde