Question

For the underlined species, n- factor is:
$I_{2} \, \left(a q\right)+\underset{— }{S_{2} O_{3}^{2 -}}\left(a q\right) \rightarrow 2I^{-}\left(a q\right)+S_{4}O_{6}^{2 -}\left(a q\right)$

• A. 1
• B. 1.5
• C. 2
• D. 2.5

Answer 1

Answer: (A)

The oxidation state of sulfur changes from +2 to +2.5 for one sulfur atom, i.e. an increase of 0.5 for one sulfur atom.
There are two sulfur atoms in the reactant, hence the total increase in oxidation state will be 0.5 x 2 = 1. Thus the n factor for the reactant is 1.