Which of the following is always negative for an exothermic reaction?

The volume of $100 \ L$ of gas increases to $120 \ L$ at a constant temperature and an external pressure of $10 \ bar$. Calculate the work done by the system. [Given: $1 \ L \ bar = 24.21 \ cal$] (in $cal$)

Work done during isothermal expansion of $1 \, \text{mole}$ of an ideal gas from $10 \, \text{atm}$ to $1 \, \text{atm}$ at $300 \, \text{K}$ is ....... $\text{cal}$ (Gas constant $R = 2 \, \text{cal} \, \text{K}^{-1} \, \text{mol}^{-1}$) (in $.8$)

Find the constant external pressure required to expand a gas from $2.5 \ L$ to $4.5 \ L$ if the amount of work done is $500 \ J$ at $298 \ K$. (in $bar$)

Which of the following is true for the value of $\Delta H - \Delta U$ at constant volume?

What is a $System$ in thermodynamics?