Balance the following equation by oxidation number method:

$SnO subscript 2 space plus space straight C space rightwards arrow space space space Sn space plus space CO$

Solution

(i) The Skeleton equation along with oxidation number of each atom is
+4 -2 0 0 +2 -2
Sn O₂ + C $rightwards arrow$ Sn+ C O
(ii) Noting the change in O.N. of above atoms,
Increase C = 0 to +2 i.e. 2
Decrease Sn = +4 to 0 i.e. 4
(iii) Equalise the increase/decrease in O.N. by multiplying SnO₂ by 1 and C by 2
SnO₂ + 2C $rightwards arrow$ Sn + CO
(iv) On counting and balancing the atoms on both sides, we get the balanced equation:
SnO₂ + 2C $rightwards arrow$ Sn + 2CO