Which of the following expressions represents the first law of thermodynamics?

The temperature of the system decreases in an

For the reaction $N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)$ at constant temperature and pressure,if $\Delta H$ and $\Delta U$ are the enthalpy and internal energy changes for the reaction,which of the following equations is correct?

Two vessels $A$ and $B$ are connected via a stopcock. Vessel $A$ is filled with a gas at a certain pressure. The entire assembly is immersed in water and allowed to reach thermal equilibrium. After opening the stopcock,the gas from vessel $A$ expands into vessel $B$,and no change in temperature is observed. Which of the following statements is true?

When a system expands under adiabatic conditions,what happens to its internal energy?

Identify from the following reactions the one that exhibits negative work done by the system.