Question

Balance the following ionic equation for a redox reaction, using whole number coefficients.

MnO4-(aq)+SO2−3(aq)+H3O+(aq)⟶Mn2+(aq)+SO2−4(aq)+H2O(l)

In the balanced equation, what is the coefficient for H2O?

(this is the exact equation in the textbook)

Answer 1

Step-by-step explanation:

In a chemical reaction equation, if number of atoms on the reactant side are equal to the number of atoms on product side then it is known as a balanced equation.

And, a redox reaction is defined as the reaction where there occurs change in the oxidation states of the reactants.

For example,
`MnO^(-)_(4)(aq) + SO^(2-)_(3)(aq) + H_(3)O^(+)(aq) \rightarrow Mn^(2+)(aq) + SO^(2-)_(4)(aq) + H_(2)O(l)`

Reduction-half reaction:
`8H_(3)O^(+) + MnO^(-)_(4) + 5e^(-) \rightarrow Mn^(2+) + 12H_(2)O` ....... (1)

Oxidation-half reaction:
`SO^(2-)_(3) + 3H_(2)O \rightarrow SO^(2-)_(4) + 2e^(-) + 2H_(3)O^(+)` ............. (2)

Now, we multiply equation (1) by 2 and multiply equation (2) by 5.

`16H_(3)O^(+) + 2MnO^(-)_(4) + 10e^(-) \rightarrow 2Mn^(2+) + 24H_(2)O` ......... (3)

`5SO^(2-)_(3) + 15H_(2)O \rightarrow 5SO^(2-)_(4) + 10e^(-) + 10H_(3)O^(+)` ......... (4)

Now, add both of equations (3) and (4) and the balance equation will be as follows.

`2MnO^(-)_(4)(aq) + 5SO^(2-)_(3)(aq) + 6H_(3)O^(+)(aq) \rightarrow 2Mn^(2+)(aq) + 5SO^(2-)_(4)(aq) + 9H_(2)O(l)`

Hence, the coefficient of
`H_(2)O` is 9.