Which among the following is $TRUE$ for an isobaric process?

Consider the reaction at $298 \ K$:
$H_{2(g)} + Cl_{2(g)} \to 2HCl_{(g)}, \Delta H^o = -185 \ kJ$
What is $\Delta U^o$ for this reaction? .....$kJ$

According to the first law of thermodynamics,which of the following is correct? (Where $q =$ heat supplied to the system and $W =$ work done by the system)

$A$ system receives $100 \ cal$ of heat,and at the same time,$50 \ cal$ of work is done by the system. Calculate the change in internal energy. (in $cal$)

The gas absorbs $100 \ J$ and is simultaneously compressed by a constant external pressure of $1.50 \ atm$ from $8 \ L$ to $2 \ L$ volume. Hence $\Delta U$ will be ..... $J$.

For the gas phase reaction $A_{2(g)} + B_{2(g)} \rightarrow 2AB_{(g)}$ taking place at constant pressure and temperature where all gases behave ideally, which of the following must be correct?