Question:

Given : \(X\,\mathrm{Na_2HAsO_3} + Y\,\mathrm{NaBrO_3} + Z\,\mathrm{HCl} \rightarrow \mathrm{NaBr} + \mathrm{H_3AsO_4} + \mathrm{NaCl}\)
The values of X, Y and Z in the above redox reaction are respectively :

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Balance electrons: As goes from +3 to +5 (2 e\(^-\) lost) and Br from +5 to \(-1\) (6 e\(^-\) gained).
Updated On: Oct 31, 2026
  • 2, 1, 2
  • 2, 1, 3
  • 3, 1, 6
  • 3, 1, 4
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The Correct Option is C

Solution and Explanation

Oxidation number change: As in \(\mathrm{Na_2HAsO_3}\) is +3 and in \(\mathrm{H_3AsO_4}\) is +5, so loss of 2 e\(^-\) per As. Br in \(\mathrm{NaBrO_3}\) is +5 and in NaBr is \(-1\), so gain of 6 e\(^-\) per Br.
Equalise electrons: \(2X = 6Y\Rightarrow X : Y = 3 : 1\), i.e. X = 3, Y = 1.
Na balance: left \(2X + Y = 7\); right NaBr (1) + NaCl (n) gives n = 6 NaCl.
Cl balance: Z = 6.
Check H: left \(3 + 6 = 9\); right \(3\times3 = 9\). O: left \(9+3 = 12\); right \(12\). Balanced.
\(3\,\mathrm{Na_2HAsO_3} + \mathrm{NaBrO_3} + 6\,\mathrm{HCl}\rightarrow \mathrm{NaBr} + 3\,\mathrm{H_3AsO_4} + 6\,\mathrm{NaCl}\).
Answer: (3) 3, 1, 6
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