The enthalpies of all elements in their standard states are:

The internal energy of a substance

Calculate the work done in joule if $1 \ mole$ of ideal gas is compressed from $25 \ dm^3$ to $13 \ dm^3$ at constant external pressure $4 \ bar$. (in $J$)

Two moles of an ideal gas are compressed isothermally and reversibly from $40 \ L$ to $20 \ L$ at $300 \ K$. What is the work done (in $kJ$)? $(R=8.314 \ J \ K^{-1} \ mol^{-1})$

What is the value of the standard enthalpy of formation of dihydrogen $(H_2)$?

What are extensive properties?