WAEC - Biology (2015 - No. 16)
A student used the following steps in testing for a non-reducing sugar.
I. added Benedict's solution to the sugar solution
ll. added dilute hydrochloric acid to the sugar and boiled it;
lll. added sodium hydroxide solution to the solution in ll. and boiled;
IV. added Benedict's solution to the cooled solution in lll.
Use this information above to answer the question.
What is the importance of step ll in the testing process? To
I. added Benedict's solution to the sugar solution
ll. added dilute hydrochloric acid to the sugar and boiled it;
lll. added sodium hydroxide solution to the solution in ll. and boiled;
IV. added Benedict's solution to the cooled solution in lll.
Use this information above to answer the question.
What is the importance of step ll in the testing process? To
neutralize the sugar solution
soften the sugar solution
change the colour of the sugar solution
increase the acid content of the sugar solution
Explanation
Dilute hydrochloric acid (HCl) is added to a non-reducing sugar solution and then boiled to hydrolyze (break down) the glycosidic bonds that link the monosaccharide units, converting the non-reducing sugar into reducing sugars, which can then react with Benedict's reagent. The HCl provides the acidic environment necessary for this hydrolysis to occur efficiently while heating accelerates the hydrolysis reaction, ensuring that the non-reducing sugar is broken down into its constituent monosaccharides (reducing sugars).
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