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

Explain enthalpy changes during phase transformations.

For one mole of an ideal gas,which of these statements must be true?
$(a)$ $U$ and $H$ each depend only on temperature.
$(b)$ Compressibility factor $Z$ is not equal to $1$.
$(c)$ $C_{P,m} - C_{V,m} = R$
$(d)$ $dU = C_V dT$ for any process.

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 $kJ$)? $(R=8.314 \ J \ K^{-1} \ mol^{-1})$

Five moles of an ideal gas at $1 \ bar$ and $298 \ K$ is expanded into vacuum to double the volume. The work done is :-

The enthalpy change of a reaction does not depend on