Balance the following oxidation-reduction reactions, which occur in acidic solution, using the half-reaction method. (Use the lowest possible coefficients. Include states-of-matter under the given conditions in your answer.
H3AsO4(aq) + Zn(s) → AsH3(g) + Zn2+(aq)
See your post above.
To balance oxidation-reduction reactions in acidic solution using the half-reaction method, we need to follow these steps:
Step 1: Identify the oxidation and reduction half-reactions.
Step 2: Balance the atoms in the half-reactions, excluding O and H.
Step 3: Balance the oxygen atoms by adding H2O to the appropriate side.
Step 4: Balance the hydrogen atoms by adding H+ to the appropriate side.
Step 5: Balance the charges by adding electrons (e-) to one side.
Step 6: Make the total number of electrons transferred equal in both half-reactions.
Step 7: Combine the half-reactions, canceling out any spectator ions or molecules.
Step 8: Verify the balanced equation.
Now, let's follow these steps to balance the given oxidation-reduction reaction:
Step 1: Identify the oxidation and reduction half-reactions.
Oxidation Half-Reaction:
Zn(s) → Zn2+(aq) + 2e-
Reduction Half-Reaction:
H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l)
Step 2: Balance the atoms in the half-reactions, excluding O and H.
Oxidation Half-Reaction: Zn(s) → Zn2+(aq) + 2e-
Reduction Half-Reaction: H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l)
Step 3: Balance the oxygen atoms by adding H2O to the appropriate side.
Oxidation Half-Reaction: Zn(s) → Zn2+(aq) + 2e-
Reduction Half-Reaction: H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l)
Step 4: Balance the hydrogen atoms by adding H+ to the appropriate side.
Oxidation Half-Reaction: Zn(s) → Zn2+(aq) + 2e-
Reduction Half-Reaction: H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l)
Step 5: Balance the charges by adding electrons (e-) to one side.
Oxidation Half-Reaction: Zn(s) → Zn2+(aq) + 2e-
Reduction Half-Reaction: H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l) + 8e-
Step 6: Make the total number of electrons transferred equal in both half-reactions.
Multiply the oxidation half-reaction by 4 and the reduction half-reaction by 1 to make the number of electrons equal:
4Zn(s) → 4Zn2+(aq) + 8e-
H3AsO4(aq) + 8H+ + 8e- → AsH3(g) + 4H2O(l) + 8e-
Now, the total number of electrons transferred is equal in both half-reactions.
Step 7: Combine the half-reactions, canceling out any spectator ions or molecules.
4Zn(s) + H3AsO4(aq) + 8H+ → 4Zn2+(aq) + AsH3(g) + 4H2O(l)
Step 8: Verify the balanced equation.
The final balanced equation is:
4Zn(s) + H3AsO4(aq) + 8H+ → 4Zn2+(aq) + AsH3(g) + 4H2O(l)
Note: The states of matter are included in the final balanced equation. (s) represents solid, (aq) represents aqueous, and (g) represents gas.