When the following redox equation is balanced with smallest whole number coefficients, the coefficient for the hydrogen sulfate (HSO4-) ion will be ______ .
Al + HSO4- + OH- --> Al2O3 + S2- + H2O (basic solution)
Here are rules for balancing redox equations but if you will tell me where you are stuck I can help you through that part.
http://www.chemteam.info/Redox/Redox.html
To balance a redox equation in basic solution, you need to follow these steps:
Step 1: Split the equation into two half-reactions. One for the oxidation half-reaction and one for the reduction half-reaction.
Oxidation half-reaction: Al → Al2O3
Reduction half-reaction: HSO4- + OH- → S2- + H2O
Step 2: Balance the atoms in each half-reaction by adding the appropriate coefficients.
Oxidation half-reaction: 2Al → Al2O3
Reduction half-reaction: 8HSO4- + 2OH- → S2- + 4H2O
Step 3: Balance the charges in each half-reaction by adding electrons (e-) if necessary.
Oxidation half-reaction: 2Al → Al2O3 + 6e-
Reduction half-reaction: 8HSO4- + 2OH- + 6e- → S2- + 4H2O
Step 4: Multiply each half-reaction by a factor to equalize the number of electrons transferred. In this case, we need to multiply the oxidation half-reaction by 3 and the reduction half-reaction by 2 to get equal numbers of electrons.
3(2Al → Al2O3 + 6e-) becomes 6Al → 3Al2O3 + 18e-
2(8HSO4- + 2OH- + 6e- → S2- + 4H2O) becomes 16HSO4- + 4OH- + 12e- → 2S2- + 8H2O
Step 5: Combine the half-reactions by canceling out the electrons.
6Al + 16HSO4- + 4OH- → 3Al2O3 + 2S2- + 18H2O
The coefficient for the hydrogen sulfate (HSO4-) ion in the balanced equation is 16.
To balance the redox equation in a basic solution, we need to follow these steps:
Step 1: Write down the unbalanced equation:
Al + HSO4- + OH- → Al2O3 + S2- + H2O
Step 2: Separate the equation into two half-reactions, one for the oxidation and one for the reduction:
Oxidation half-reaction: Al → Al2O3
Reduction half-reaction: HSO4- + OH- → S2- + H2O
Step 3: Balance the atoms other than hydrogen and oxygen in each half-reaction:
Al → Al2O3 (already balanced)
HSO4- + OH- → S2- + H2O (balanced)
Step 4: Balance oxygen atoms by adding water (H2O) to the side that needs more oxygen:
Al → Al2O3 (already balanced)
HSO4- + OH- → S2- + H2O + H2O
Step 5: Balance hydrogen atoms by adding hydrogen ions (H+) to the side that needs more hydrogen:
Al → Al2O3 (already balanced)
HSO4- + OH- + H+ → S2- + H2O + H2O
Step 6: Balance the charges by adding electrons (e-) to the side with the more positive charge:
Al → Al2O3 (already balanced)
HSO4- + OH- + H+ + e- → S2- + H2O + H2O
Step 7: Determine the total number of electrons transferred by the coefficients of the species involved in the half-reactions:
For the reduction half-reaction: 1 electron (e-)
Step 8: Equate the number of electrons transferred in both half-reactions:
Al → Al2O3 (already balanced)
1 Al2O3 + 3 HSO4- + 3 OH- + 3 H+ + 3 e- → 3 S2- + 6 H2O
Step 9: Multiply each half-reaction by the necessary coefficient to make the number of electrons equal in both half-reactions:
2 Al + 6 HSO4- + 6 OH- + 6 H+ + 6 e- → 3 Al2O3 + 9 S2- + 18 H2O
Step 10: Simplify and cancel out any common terms:
2 Al + 6 HSO4- + 6 OH- + 6 H+ + 6 e- → 3 Al2O3 + 9 S2- + 18 H2O
The coefficient for the hydrogen sulfate (HSO4-) ion is 6.