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WAEC Biology 2015 Question 22

Question 22

Food Substances and Enzymes

A student used the following steps in testing for a non-reducing sugar: I. added Benedict's solution to the sugar solution; II. added dilute hydrochloric acid to the sugar solution and boiled it; III. added sodium hydroxide solution to the solution in II and boiled; IV. added Benedict's solution to the cooled solution in III.
Why did the student add the dilute hydrochloric acid to the sugar solution in step II? To

  1. A.oxidize the sugar solution.
  2. B.hydrolyse the sugar solution.
  3. C.dry the sugar solution.
  4. D.increase the volume of the sugar solution.
Show the answer and explanation

Answer: B (hydrolyse the sugar solution.)

Explanation

Boiling with dilute acid hydrolyses (breaks down) a non-reducing sugar such as sucrose into reducing sugars (glucose and fructose), which can then react with Benedict's solution.