Balancing Redox Reactions

10 H+ + NO3− → NH4+ + 3 H2O Select the half-reaction that has the correct number of electrons, on the correct side, in order to balance the reaction.

10 H+ + NO3− + 8 e− → NH4+ + 3 H2O

Assume you are in the process of balancing the half-reaction listed below. At this point, all of the atoms are balanced, but the charge needs to be balanced. You will complete this step by adding electrons to one side of the equation. 10 H+ + NO3− → NH4+ + 3 H2O Select the half-reaction that has the correct number of electrons, on the correct side, in order to balance the reaction.

10 H+ + NO3− + 8 e− → NH4+ + 3 H2O

What is the coefficient for H2O when NH3 + NO2 → N2 is balanced in acid?

12

What is the coefficient for H2O when NH3 + NO2 → N2 is balanced in base?

12

What is the coefficient for OH− when MnO4− + H2S → S + MnO is balanced in base?

2

What is the overall reaction for the following half-reactions? Reduction half-reaction: Ag+ + e− → Ag Oxidation half-reaction: Ni0 → Ni2+ + 2 e−

2 Ag+ + Ni → 2 Ag + Ni2+

How many electrons are needed to balance each of the following half-reactions? Reduction half-reaction: Sn2+ + __e− → Sn Oxidation half-reaction: Co → Co2+ + __e− Overall reaction: Sn2+ + Co → Sn + Co2+

2 electrons

What is the overall reaction for the following half-reactions? Reduction half-reaction: Hg2+ + 2 e− → Hg Oxidation half-reaction: Cr → Cr3+ + 3 e−

3 Hg2+ + 2 Cr → 3 Hg + 2 Cr3+

How many electrons are needed to balance each of the following half-reactions? Reduction half-reactionFe3+ + __e− → Fe Oxidation half-reaction:Al → Al3+ + __e− Overall reaction:Fe3+ + Al → Fe + Al3+

3 electrons

What is the coefficient for H2O when PbO2 + I2 → Pb2+ + IO3− is balanced in acid?

4

What is the coefficient for H2O when S2− + NO3− → S + NO is balanced in acid?

4

Assume you are in the process of balancing the half-reaction listed below. At this point, you need to begin balancing hydrogen atoms by adding hydrogen ions (H+) to one side of the equation. NO3− → NO + 2 H2O Select the half-reaction that has the correct number of hydrogen ions, on the correct side, in order to balance the reaction.

4 H+ + NO3− → NO + 2 H2O

What is the coefficient for H2O when MnO4− + H2S → S + MnO is balanced in acid?

6

What is the coefficient for OH− when PbO2 + I2 → Pb2+ + IO3− is balanced in base?

8

What is the coefficient for OH− when S2− + NO3− → S + NO is balanced in base?

8

What is the balanced reduction half-reaction for the unbalanced oxidation-reduction reaction? Na + Cl2 → NaCl

Cl2 + 2e− → 2Cl−

Assume you are in the process of balancing the half-reaction listed below. At this point, you need to begin balancing oxygen atoms by adding water to one side of the equation. Cr2O72− → 2 Cr3+ Select the half-reaction that has the correct number of water molecules, on the correct side, in order to balance the reaction. The half-reaction will not be completely balanced.

Cr2O72−→ 2 Cr3+ + 7 H2O

What substance is added to balance the hydrogen in a half-reaction?

H+

What substance is added to balance oxygen in a half-reaction?

H2O

What is the balanced half-reaction for MnO4− → Mn2+?

MnO4− + 8H+ + 5e−→ Mn2+ + 4H2O

What is the balanced oxidation half-reaction for the unbalanced oxidation-reduction reaction? Na + Cl2 → NaCl

Na → Na+ + e−