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Q)

Given the following two statements, which of the following options that follow is TRUE?

STATEMENT 1: Glucose gives a reddish-brown precipitate with Fehling’s solution.

because

STATEMENT 2: Reaction of Glucose with Fehling’s solution gives CuO and gluconic acid.

$\begin{array}{1 1} \text{(A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1} \\ \text{ (B) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1} \\ \text{ (C) Statement-1 is True, Statement-2 is False } \\ \text{ (D) Statement-1 is False, Statement-2 is True} \end{array} $

2 Answers

Comment
A)
Toolbox:
  • Fehling's test is a chemical test to detect reducing sugars and aldehydes in a solution.
Fehling's test is a chemical test to detect reducing sugars and aldehydes in a solution.
In this test the presence of aldehydes is detected by reduction of the deep blue solution of copper(II) to a red precipitate of insoluble copper oxide. The test is commonly used for reducing sugars.
Fehling's solution is Cupric Oxide CuO, which is blue in colour but changes to red colour precipitate of Cuprous Oxide.
This is illustrated as follows: $C_6H_12O_6$ (Glucose) $+2CuO$ (Cupric Oxide) $\rightarrow C_6H11O5COOH$ (Gluconic Acid) $+ Cu_2O$ (Cuprous Oxide)
We see therefore that Statement 1 is true but Statement 2 is False.
 
Comment
A)
Glucose contains an Aldehyde group. It reduces Fehling's solution to give red precipitate of $Cu_2O$
$C_6H_{12}O_6$+Fehling solution →$(H_6O_{11}C_7)^−+Cu_2O$↓
$\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;Red \; precipitate$
Hence statement 1 is True and 2 is False
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