Question

In the following reaction :
$NO _3^{\ominus}+ As _2 S _3+ H _2 O \rightarrow AsO _4^{3-}+ NO + SO _4^{2-}+ H ^{\oplus}$
The equivalent weight of $As _2 S _3$ (with molecular weight $M$ ) is:

• A. $\frac{3 M}{28}$
• B. $\frac{M}{4}$
• C. $\frac{M}{24}$
• D. $\frac{M}{28}$

Answer 1

Answer: (D)

$NO _3{ }^{\ominus}+ As _2 S _3 \longrightarrow AsO _4{ }^{3-}+ NO + SO _4{ }^{2-}$
$As _2 S _3+20 H _2 O \longrightarrow 2 AsO _4{ }^{3-}+3 SO _4{ }^{2-}+40 H ^{\oplus}+28 e ^{-}$
$E_{ As _2 S _3}=\frac{ M }{28}$ (nfactor $=28$ ) (electrons lost/mol)