Question

Determine the correctness or otherwise of the following Assertion [a] and Reason [r]:
[a]: A partially scoured cotton fabric bleached with H$_2$O$_2$ exhibits higher water absorbancy than that bleached with NaClO$_2$.
[r]: Bleaching with H$_2$O$_2$ also facilitates scouring.

• A. Both [a] and [r] are true and [r] is the correct reason for [a]
• B. Both [a] and [r] are true but [r] is not correct reason for [a]
• C. Both [a] and [r] false
• D. [a] is true but [r] is false

Hint:

When comparing bleaching routes on cotton, remember the medium: alkaline peroxide often adds scouring (better wettability), whereas acidic chlorite mainly bleaches color without removing waxes.

Answer 1

The Correct Option is A

Step 1: Process chemistry of H$_2$O$_2$ bleaching
Cotton peroxide bleaching is carried out in alkaline medium (typically NaOH with stabilizer and wetting agent). Under alkaline conditions, peroxide not only decolorizes chromophores but also continues scouring: it helps saponify residual waxes/fats and breaks down pectins/hemicelluloses. This removes hydrophobic impurities and increases surface hydrophilicity/wetting.
Step 2: Process chemistry of NaClO$_2$ bleaching
Sodium chlorite bleaching is done in acidic medium. It is highly effective for decolorization (especially lignin‐type impurities) but provides little to no additional scouring action; waxy residues are not efficiently removed in acid conditions. Thus, on partially scoured cotton, residual hydrophobes remain, limiting absorbency.
Step 3: Link reason to assertion
Because H$_2$O$_2$ bleaching simultaneously advances scouring (Reason true), a partially scoured cotton subjected to H$_2$O$_2$ will lose more hydrophobic matter than one bleached with NaClO$_2$, yielding higher water absorbancy (Assertion true). Therefore, [r] correctly explains [a].
Final Answer: Both [a] and [r] are true, and [r] is the correct reason for [a].