$A$ certain mass of an ideal gas absorbs $80 \ kJ$ heat and the gas is expanded from $2 \ L$ to $10 \ L$ at a constant pressure of $25 \ bar$. What is $\Delta U$ for the gas in the process in $kJ$? $(1 \ bar-L = 100 \ J)$

$A$ gas in a frictionless piston cylinder at a constant pressure of $1 \ atm$ expands from a volume of $2 \ L$ to $6 \ L$. In doing so,it absorbs $800 \ J$ of heat from the surroundings. The change in internal energy of the process is ..... $J$.

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?

What is the value of the increase in internal energy when a system does $8 \ J$ of work on the surroundings by supplying $40 \ J$ of heat to it (in $J$)?

$2 \ mol$ of an ideal gas are expanded isothermally and reversibly from $20 \ L$ to $40 \ L$ at $300 \ K$. Calculate work done. $(R=8.314 \ J \ K^{-1} \ mol^{-1})$ (in $J$)

$A$ gas expands from a volume of $1 \text{ dm}^3$ to $1.25 \text{ dm}^3$ against a constant external pressure of $1 \text{ bar}$. Calculate the change in internal energy $(\Delta U)$ if $150 \text{ J}$ of heat is supplied to the system. (in $\text{ J}$)