The standard enthalpy is zero for the substance

The standard molar enthalpy of a substance is the enthalpy of the substance at…………..pressure and at specified temperature.

The standard molar enthalpy of a substance is the enthalpy of the substance at…………..pressure and at specified temperature.

For which of the following the standard enthalpy is not zero?

Why standard entropy of an elementary substance is not zero whereas standard enthalpy of formation is taken as zero?

Which of the following element standard enthalpy is not to be equal to zero?

The standard enthalpy of diamond is zero at 298K and 1 atm pressure.

The standard enthalpy of diamond is zero at 298K and 1 atm pressure.