What is the change in internal energy when a system releases $8 \ kJ$ of heat and performs $660 \ J$ of work on the surroundings (in $J$)?

When one mole of $NH_3$ gas and one mole of $HCl$ gas are mixed in a closed container to form ammonium chloride gas,which of the following is true?

For the reaction $CO_{(g)} + \frac{1}{2} O_{2(g)} \rightarrow CO_{2(g)}$ at constant temperature and pressure,which of the following statements is correct?

The volume of a gas at $STP$ is $1.5 \ L$. When $300 \ J$ of heat is supplied to it at $1 \ atm$ pressure,its volume becomes $2 \ L$. What is the value of $\Delta U$ in $J$ for this process? $(1 \ L \cdot atm = 101 \ J)$

An engine absorbs heat $Q_1$ at temperature $T_1$ and heat $Q_2$ at temperature $T_2$. The work done by the engine is given as $W = Q_1 + Q_2$. Which of the following statements is correct?

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: $R = 8.3 \ J \ mol^{-1} \ K^{-1}$]