WAEC Chemistry 2021 Theory — Question 20
Question 20 of 31 from the West African Examinations Council (WAEC) Chemistry 2021 Theory paper, with the correct answer and a full explanation.
Advertisement
3(c-ii). Consider the organic compound CH3CH2CH=CHCOOH. (i) State two chemical reactions that could be used to identify the compound. (ii) What would be observed in each of the reactions stated in (i)?
Model answer
(i) Reaction with bromine water/CCl4-bromine; reaction with acidified potassium dichromate(VI) (K2Cr2O7/H+); reaction with acidified/aqueous NaHCO3 or Na2CO3. (ii) The compound decolourises bromine water/CCl4-bromine (unsaturation test); it changes acidified K2Cr2O7 from orange to green, and changes H+/KMnO4 from purple to colourless (oxidation of the double bond); it produces effervescence (gas evolution) with NaHCO3(aq), confirming the carboxylic acid (-COOH) group.
Advertisement
Sign up free to unlock
- Score tracking
- Practice history
- Saved questions
- Progress dashboard
- Personalized sessions
- Weak-topic breakdown
…and/or go further with premium services and No Ads.