Answer :
The standard value for temperature T in the Nernst equation is 25°C (298 K). This temperature is commonly used since standard-state values in thermodynamics are typically listed at this temperature.
The standard value for T in the common form of the Nernst equation is 25°C, which is equivalent to 298 K. This value is often used because most thermodynamic tables list the standard-state values at 298.15 K (or 25° C), and it's a common assumption that reactions or processes are taking place under so-called 'room temperature' conditions.
The Nernst equation itself indicates that cell potential is dependent on concentration, and it fundamentally relates the voltage of an electrochemical cell to the concentrations of reactants and products at a given temperature.
