Using the set of smallest possible integer coefficients to balance the redox equation
H2O2 +MnO−4 -> O2 +Mn+2
(acidic solution), the coefficient for H2O2 is
1. 5.
2. The correct coefficient is not given.
3. 2.
4. 7.
5. 4.
To balance a redox equation, you need to follow certain steps:
1. Assign oxidation numbers to all the elements in the equation.
2. Identify which elements are being oxidized and which are being reduced.
3. Write separate half-reactions for oxidation and reduction.
4. Balance the atoms in each half-reaction by adjusting the coefficients.
5. Balance the charge in each half-reaction by adding electrons (e-) as needed.
6. Multiply the half-reactions by integers, if necessary, to make the number of electrons equal in both reactions.
7. Combine the two half-reactions so that the electrons cancel out.
8. Check that the atoms and charges are balanced in the balanced redox equation.
Now, let's apply these steps to balance the given redox equation: H2O2 + MnO−4 -> O2 + Mn+2 (acidic solution).
1. Assign oxidation numbers:
The oxidation number of H in H2O2 is +1.
The oxidation number of O in H2O2 is -1.
The oxidation number of Mn in MnO−4 is +7.
The oxidation number of O in MnO−4 is -2.
2. Identify the oxidation and reduction:
In this equation, H2O2 is being reduced (gaining oxygen) from an oxidation state of -1 to 0 in O2, while MnO-4 is being oxidized (losing oxygen) from an oxidation state of +7 to +2 in Mn+2.
3. Write separate half-reactions:
Reduction half-reaction: H2O2 -> O2
Oxidation half-reaction: MnO−4 -> Mn+2
4. Balance the atoms in each half-reaction:
Reduction half-reaction: 2H2O2 -> O2 (since there are 2 O atoms on the reactant side and 2 O atoms on the product side)
Oxidation half-reaction: MnO−4 -> Mn+2 + 4O2- (since there is 1 Mn atom on the reactant side and 1 Mn atom on the product side, and 4 O atoms on the reactant side and 4 O atoms on the product side)
5. Balance the charge in each half-reaction:
To balance the charge in the oxidation half-reaction, we need to add 8 e- to the product side:
MnO−4 -> Mn+2 + 4O2- + 8e-
6. Multiply the half-reactions by integers, if necessary, to make the number of electrons equal:
To make the number of electrons equal in both half-reactions, we need to multiply the oxidation half-reaction by 5:
5MnO−4 -> 5Mn+2 + 20O2- + 40e-
7. Combine the half-reactions:
Now, combine the two half-reactions, making sure the number of electrons cancel out:
2H2O2 + 5MnO−4 -> O2 + 5Mn+2 + 2H2O
8. Check that the atoms and charges are balanced:
The balanced equation is: 2H2O2 + 5MnO−4 -> O2 + 5Mn+2 + 2H2O
Therefore, the coefficient for H2O2 is 2. So the correct answer is option 3.