Question

How can I balance the galvanic cell equation?

Answer 1

Galvanic cell is known as the electrochemical cell. It has the tendency to convert the chemical energy of the spontaneous redox reaction into the electrical energy. This cell is also known as voltaic cell. It uses chemical reactions for the generation of electrical energy. In the redox reactions the electrons are transferred so the energy is released when the reaction occurs spontaneously.

Complete step-by-step answer: So the reactions which are used in the galvanic cells are the following two halfs reactions. So look at the following reaction:
${{O}_{2}}+4{{H}^{+}}+4{{e}^{-}}\to {{H}_{2}}O$
$N{{i}^{2+}}+2{{e}^{-}}\to Ni$
So now let us reverse one of the two half reactions so that the cell voltage get positive. So we are reversing the nickel half reaction. So now the cell reactions will be the following:
${{O}_{2}}+4{{H}^{+}}+4{{e}^{-}}\to {{H}_{2}}O$
$Ni\to N{{i}^{2+}}-2{{e}^{-}}$
Now as we see that in the oxygen half reaction the electrons involved are 4 but in the nickel half reaction the electrons involved are 2, so to equalise the electrons we will multiply the nickel half reaction by 2. So now the reactions will be the following:
${{O}_{2}}+4{{H}^{+}}+4{{e}^{-}}\to {{H}_{2}}O$
$2Ni\to 2N{{i}^{2+}}-4{{e}^{-}}$
Now add both of the half reactions. So on adding we will get the following reaction:
${{O}_{2}}+2Ni+4{{H}^{+}}\to 2N{{i}^{2+}}+2{{H}_{2}}O$
So now we will check whether the mass balances both sides. So on the reactants side there are 2 atoms of oxygen, two nickel atoms and 4 hydrogen. Whereas on the product side we have 2 atoms of oxygen, two nickel atoms and 4 hydrogen that means the mass is balanced.
Now let us check whether the charge is balanced or not. So on the reactant side the charge is 4+ on hydrogen and on the product side the charge is 4+ on nickel that means the charge is also balanced.
So the reaction is balanced.

Note: In the galvanic cell the oxidation occurs at anode and reduction occurs at cathode. The salt bridge is used in galvanic cells which contain electrolytes as it is required to complete the circuit. The presence of an external circuit helps in conducting the flow of electrons between the electrodes.