Enthalpy is a state function. Standard enthalpy change is measured at:

Explanation

The correct option for the temperature at which the standard enthalpy change is measured is C) 298K (Kelvin). This is the most commonly used temperature for standard conditions in thermochemistry. Standard enthalpy change (ΔH°) is typically measured at a standard temperature of 298.15 Kelvin (25 degrees Celsius or 77 degrees Fahrenheit). This standard temperature is often used in thermochemical calculations to provide a consistent reference point for measuring enthalpy changes, particularly in chemical reactions. The standard enthalpy change is often expressed in units of kilojoules per mole (kJ/mol) or calories per mole (cal/mol).