$2.5 \ kJ$ of work is done on the system and it releases $1500 \ J$ of heat. What is the change in internal energy (in $J$)?

For water $\Delta_{vap} H = 41 \ kJ \ mol^{-1}$ at $373 \ K$ and $1 \ bar$ pressure. Assuming that water vapour is an ideal gas that occupies a much larger volume than liquid water,the internal energy change during evaporation of water is $...... \ kJ \ mol^{-1}$.
[Use: $R = 8.3 \ J \ mol^{-1} \ K^{-1}$]

$A$ gas is allowed to expand in an insulated container against a constant external pressure of $2.5 \ atm$ from $2.5 \ L$ to $4.5 \ L$. The change in internal energy of the gas in joules is: (in $J$)

The law of conservation of energy states that

For the reaction $C_{(s)} + \frac{1}{2}O_{2(g)} \to CO_{(g)}$ at constant $T$ and $P$,which of the following statements is correct?

If the initial internal energy of a system is $U_1$,and it absorbs $450 \ J$ of heat from the surroundings and performs $600 \ J$ of work,what will be the final internal energy of the system?