Question

The enthalpies of the elements in their standard states are assumed to be:

• A. zero at 298 K
• B. unit at 298 K
• C. zero at all temperatures
• D. zero at 273 K

Answer 1

The correct option is A zero at 298 K

The enthalpies of the element in their standard states are assumed to be zero at 298 K. At standard state, all elements have zero enthalpies of formation ( elements like oxygen, nitrogen in the form of gases, solid carbon in form of graphite etc).

Hence, option A is correct.