Which of the following is the correct mathematical expression for the first law of thermodynamics?

$A$ gas expands isothermally against a constant external pressure of $1 \ bar$ from $10 \ dm^3$ to $20 \ dm^3$ by absorbing $800 \ J$ of heat from the surroundings. Calculate the value of $\Delta U$. (in $J$)

$q$ and $w$ are both ....... functions and $q + w$ is a ....... function.

When $500 \ J$ of heat is supplied to a system at constant volume,the temperature of the system increases from $20^oC$ to $25^oC$. The change in internal energy of the system is ...... $J$.

What is the final temperature of $0.10 \ mol$ monoatomic ideal gas that performs $75 \ cal$ of work adiabatically if the initial temperature is $227 \ ^\circ C$? (Use $R = 2 \ cal \cdot K^{-1} \cdot mol^{-1}$)

The temperature of the system decreases in an