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

Which among the following is $NOT$ a feature of a reversible process?

What is the value of $\Delta H - \Delta U$ for the following reaction? $2 C_{(s)} + 3 H_{2(g)} \rightarrow C_2H_{6(g)}$

What is a system? Explain the types of systems.

Choose the reaction in which $\Delta H$ is not equal to $\Delta U$.

Two moles of an ideal gas is expanded isothermally from a volume of $300 \ cm^3$ to $2.5 \ dm^3$ at $298 \ K$ against a constant pressure of $1.9 \ bar$. Calculate the work done in joules. (in $J$)