Question

How would you balance the following equation: S+HNO3 --> H2SO4+NO2+H2O?

Answer 1

By a redox reaction. Sulfur is oxidized to sulfate; nitrate is reduced to nitric oxide:

`S(s) + 6NO_3^(-) + 4H^+ rarr 6NO_2(g)uarr + 2H_2O(l) + SO_4^(2-)`

Explanation:

Reduction:
`NO_3^(-) + 2H^(+) +e^(-) rarr NO_2(g)uarr + H_2O` `(i)`

Oxidation:
`S(s) + 4H_2O(l) rarr SO_4^(2-) + 8H^+ + 6e^-` `(ii)`

`(ii) + 6xx(i)` `=` `S(s) + 4HNO_3(aq) + 2NO_3^(-) rarr 6NO_2(g)uarr + 2H_2O(l) + SO_4^(2-)`