For a chemical reaction,when does $\Delta H = \Delta U$ occur?

At $T(K)$, $2 \ mol$ of an ideal gas is allowed to expand reversibly and isothermally from a pressure of $10 \ atm$ to $1 \ atm$. The work done (in $kJ$) is $(R=8.3 \ J \ K^{-1} \ mol^{-1})$.

The difference between $\Delta H$ and $\Delta U$ is usually significant for systems consisting of:

Energy can be transferred from a system to the surroundings as work if $.....$

The enthalpies of all elements in their standard states are:

Identify an example of an intensive property from the following: