Calculate the change in internal energy of the system if $20 \ kJ$ of work is done on the system and it releases $10 \ kJ$ of heat in a particular reaction. (in $kJ$)

Three moles of an ideal gas expand reversibly under isothermal conditions from $2 \, L$ to $20 \, L$ at $300 \, K$. The amount of heat change (in $kJ / mol$) in the process is:

At $300 \ K$,the enthalpy change for the reaction $C_3H_8(g) + 5O_2(g) \rightarrow 3CO_2(g) + 4H_2O(l)$ is $-2800 \ kJ \ mol^{-1}$. Calculate the internal energy change $(\Delta U)$ for the reaction at the same temperature.

Explain the relationship between the change in heat at constant pressure and constant volume.

Express the change in internal energy of a system when
$(i)$ No heat is absorbed by the system from the surroundings,but work $(w)$ is done on the system. What type of wall does the system have?
$(ii)$ No work is done on the system,but $q$ amount of heat is taken out from the system and given to the surroundings. What type of wall does the system have?
$(iii)$ $w$ amount of work is done by the system and $q$ amount of heat is supplied to the system. What type of system would it be?

An ideal gas expands against a constant external pressure of $2 \ bar$ from $5 \ L$ to $8 \ L$ and absorbs $10 \ kJ$ of heat. What is $\Delta U$ of the system (in $J$)?