The overpotential is the difference between the actual potential and the standard potential of a galvanic cell. It represents the extra energy required to drive the electrochemical reaction at a certain rate current . In this case, the standard potential is 1.4 V, and the actual potential is 1.6 V.To calculate the overpotential, we simply subtract the standard potential from the actual potential:Overpotential = Actual potential - Standard potentialOverpotential = 1.6 V - 1.4 VOverpotential = 0.2 VSo, the overpotential required to generate a current of 0.5 A in this galvanic cell is 0.2 V.The overpotential is necessary for the reaction to proceed at the desired rate because it helps overcome the energy barriers associated with the reaction, such as activation energy and resistive losses in the cell. These energy barriers can slow down the reaction, and by providing extra energy in the form of overpotential, we can ensure that the reaction proceeds at the desired rate in this case, generating a current of 0.5 A .