Question

Potassium permanganate, KMnO4, is a powerful oxidizing agent. The products of a given redox reaction with the permanganate ion depend on the reaction conditions used. In basic solution, the following equation represents the reaction of this ion with a solution containing sodium sulfite:

MnO4−(aq)+SO32−(aq)→MnO2(s)+SO42−(aq)

Since this reaction takes place in basic solution, H2O(l) and OH−(aq) will be shown in the reaction. Places for these species are indicated by the blanks in the following restatement of the equation:

MnO4−(aq)+SO32−(aq)+     −−−→MnO2(s)+SO42−(aq)+     −−−

Part B

What are the coefficients of the reactants and products in the balanced equation above? Remember to include H2O(l) and OH−(aq) in the blanks where appropriate. Your answer should have six terms.

Enter the equation coefficients in order separated by commas (e.g., 2,2,1,4,4,3). Include coefficients of 1, as required, for grading purposes.

Answer 1

Balance the reaction in basic solution

so

split reaction

MnO4− --> MnO2

SO3-2 --> SO4-2

balance O adding H2O

MnO4− --> MnO2 + 2H2O

H2O + SO3-2 --> SO4-2

Balance H adding H+

4H+ + MnO4− --> MnO2 + 2H2O

H2O + SO3-2 --> SO4-2 + 2H+

blance charges

3e- + 4H+ + MnO4− --> MnO2 + 2H2O

H2O + SO3-2 --> SO4-2 + 2H+ + 2e-

balance e-

6e- + 8H+ + 2MnO4− --> 2MnO2 + 4H2O

3H2O + 3SO3-2 --> 3SO4-2 + 6H+ + 6e-

add all

6e- + 8H+ + 2MnO4− + 3H2O + 3SO3-2 --> 3SO4-2 + 6H+ + 6e- + 2MnO2 + 4H2O

cancel common terms

2H+ + 2MnO4−+ 3SO3-2 --> 3SO4-2 + 2MnO2 + H2O

add OH- to make it basic

2OH- + 2H+ + 2MnO4−+ 3SO3-2 --> 3SO4-2 + 2MnO2 + H2O + 2OH-

convert to water

2H2O + + 2MnO4−+ 3SO3-2 --> 3SO4-2 + 2MnO2 + H2O + 2OH-

cancel water

H2O + + 2MnO4−+ 3SO3-2 --> 3SO4-2 + 2MnO2 + 2OH-