Use the following steps to balance the redox reaction below:
Mg + Au+ Mg2+ + Au
a. Write the oxidation and reduction half-reactions. Make sure each half-reaction is balanced for number of atoms and charge
b. Multiply each half-reaction by the correct number, in order to balance charges for the two half-reactions.
c. Add the equations and simplify to get a balanced equation.
To balance the redox reaction, follow these steps:
a. Write the oxidation and reduction half-reactions:
First, identify the species that are being oxidized and reduced. In this case, magnesium (Mg) is being oxidized from a neutral state (0 charge) to a +2 charge, and gold (Au+) is being reduced from a +1 charge to a neutral state (0 charge).
Oxidation half-reaction:
Mg -> Mg2+ (balanced for atoms)
Reduction half-reaction:
Au+ -> Au (balanced for atoms)
Now, balance the charges in each half-reaction:
Oxidation half-reaction:
Mg -> Mg2+ + 2e- (balanced for charge)
Reduction half-reaction:
Au+ + e- -> Au (balanced for charge)
b. Multiply each half-reaction by the correct number to balance charges for the two half-reactions:
Multiply the oxidation half-reaction by 2 to balance the number of electrons:
2Mg -> 2Mg2+ + 4e-
Now, the number of electrons in the oxidation and reduction half-reactions is balanced.
c. Add the equations and simplify to get a balanced equation:
Add the oxidation and reduction half-reactions:
2Mg + Au+ -> 2Mg2+ + Au
Simplify the equation, if needed. In this case, the equation is already balanced, so no further simplification is required.
The balanced equation for the redox reaction is:
2Mg + Au+ -> 2Mg2+ + Au
Mg to Mg2+ loses 2 electrons
Au+ to Au gains one electron. So 2Au for each Mg
Mg yields Mg+ +2e
Au+ + e yields Au
so multiply the second equation by 2