Problem #$2$

A gas is contained in a piston$-$cylinder device and undergoes a thermodynamic process. Initially, the gas has an internal energy of $300$ J$.$ During the process:

The gas absorbs $Q=150J$ of heat from the surroundings.

$W=50J$ of work is done by the gas on the piston.

Questions:

Change in Internal Energy $($work is done $\text{'}$by$\text{'}$ the gas$)$ :

$($a$)$ Use the First Law of Thermodynamics to calculate the change in the gas's internal energy $(U).$

$($b$)$ What is the final internal energy of the gas?

Reverse Process $($work is done $\text{'}$on$\text{'}$ the gas$)$ :

If the process is reversed $($the gas does $-50$ J of work on the surroundings and releases $-150$ J of heat$),$ what will be the final internal energy of the gas?

Isothermal Expansion:

If the process occurs isothermally $($constant temperature$),$ and the work done by the gas is $200$ J $,$ how much heat must the gas absorb$?$