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JAMB Chemistry 2017 past questions and answers

2 questions. Try each one, then open the answer to check yourself and read the explanation.

Question 2

Solubility and Solutions

At room temperature (300 K) in fig 1

Diagram for this question
  1. A.Y is twice as soluble as X.
  2. B.X is twice as soluble as Y
  3. C.X and Y are soluble to the same extent
  4. D.X is three times as soluble as Y
Show the answer and explanation

Answer: A (Y is twice as soluble as X.)

Explanation

Reading the graph at 300 K, Y dissolves about 40 g per 100 g of water and X about 20 g, so Y is twice as soluble as X.

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Question 22

Alkanoic Acids and Esters

The products formed on hydrolysis of CH3–C(=O)–OCH2CH2CH3 in acid (HCl) is

  1. A.CH3C(=O)–OH + CH3CH2CH2Cl
  2. B.CH3CH2CH2OH + CH3C(=O)–Cl
  3. C.CH3C(=O)–O–H + HOCH2CH2CH3
  4. D.CH3C(=O)–O–H + CH3CH3
Show the answer and explanation

Answer: C (CH3C(=O)–O–H + HOCH2CH2CH3)

Explanation

Acid hydrolysis of an ester gives back the carboxylic acid and the alkanol: propyl ethanoate gives ethanoic acid and propan-1-ol. The HCl is only a catalyst.

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