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Question

Chemistry Question on Chemical Reactions

An alkaline solution of...... and citrate ions is called:

A

silver nitrate, Fehlings solution

B

cupric sulphate, Schiffs reagent

C

silver chloride, Tollens reagent

D

cupric sulphate, Benedicts solution

Answer

cupric sulphate, Benedicts solution

Explanation

Solution

Benedicts solution: It is an alkaline solution of cupric ion complexed with citrate ions. When Benedict solution is used to oxidise an aldehyde, the complexed cupric ion (deep blue) is reduced to cuprous oxide (red). The presence of red precipitate of cuprous oxide serve as an indication of an aldehyde group in a molecule. RCHO+2Cu(OH)2+NaOHR-CHO+2Cu{{(OH)}_{2}}+NaOH\xrightarrow{{}} RCOONa+Cu2O(red)+3H2OR-COONa+\underset{(red)}{\mathop{C{{u}_{2}}O}}\,\,+3{{H}_{2}}O