AIIMS 2018 Chemistry Optical Activity Assertion Reason Question
Assertion: A solution of sucrose in water is dextrorotatory but on hydrolysis in presence of little hydrochloric acid, it becomes laevorotatory. Reason: Sucrose on hydrolysis gives unequal amounts of glucose and fructose as a result of which change in sign of rotation is observed.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
Correct Answer
Detailed Explanation
The assertion is true because a sucrose solution is indeed dextrorotatory, and upon hydrolysis in the presence of HCl, it produces glucose and fructose, leading to a change in optical rotation. However, the reason is false; sucrose hydrolysis yields equal amounts of glucose and fructose, both of which are laevorotatory, thus the change in sign of rotation is not due to unequal amounts. Option A is incorrect because the reason does not correctly explain the assertion, while option B is incorrect for the same reason. Option D is incorrect as the assertion is true.
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