Question

The enthalpies of the elements in their standard states are arbitarily assumed to be ___________.

• A. zero at 298 K and 1 atm
• B. unity at 298 K and 1 atm
• C. Zero at all temperatures
• D. zero at 273 K and 1 atm

Answer 1

The correct option is A zero at 298 K and 1 atm

The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.

At standard state, temperature and pressure are 298.15 K and 1 atm. Enthalpy is generally taken to be zero at STP.