Friedel-Crafts acylation gives acetophenone: $C_6H_6\xrightarrow{CH_3COCl/AlCl_3}C_6H_5COCH_3$. The haloform reaction with NaOCl gives $C_6H_5COONa$ (P) + $CHCl_3$ (Q). On acidification P gives benzoic acid, $C_6H_5COOH$. Chloroform on exposure to air and light forms the poisonous gas phosgene: $CHCl_3\xrightarrow{air,\ light}COCl_2$.