Enthalpy of sublimation of a substance is equal to

At constant pressure, the heat of formation of a compound is not dependent on temperature, when

When it is not possible to calculate the enthalpy of a reaction experimentally,it can be calculated by .....

Calculate the enthalpy change when $12 \ g$ of carbon reacts with sufficient hydrogen to form methane. If the enthalpy of formation of methane is $-75 \ kJ \ mol^{-1}$. (in $kJ$)

At $1 \ bar$ and $298 \ K$,the standard molar enthalpy of formation of which substance is zero?

The bond enthalpies of $H_2$,$X_2$,and $HX$ are in the ratio of $2 : 1 : 2$. If the standard enthalpy of formation of $HX$ is $-50 \ kJ \ mol^{-1}$,the bond enthalpy of $H_2$ is .... $kJ \ mol^{-1}$.