What is the normal emf of a Weston cell at 20 degree Celsius and how does the emf change when the cell is used at 0 degree?

The normal electromotive force (emf) of a Weston cell at 20 degrees Celsius is approximately 1.018 volts. When the temperature drops to 0 degrees Celsius, the emf of the cell typically decreases slightly due to the reduced activity of the electrolyte and changes in the chemical reaction dynamics. This decrease is usually around 0.001 to 0.002 volts per degree Celsius. Thus, at 0 degrees Celsius, the emf would be lower than at 20 degrees Celsius.