Question

A gas absorbs 10J of heat and is simultaneously

compressed by a const and external pressure
of 0.5 atm from 4L to 2L in volume What
is the change in the internal energy.
A. 101J b. 111J c.2J d. none of the above​

Answer 1

Given :

Heat absorbs , Q = 10 J .

Pressure ,
`P=0.5 \ atm =0.5* 101325\ Pa`

Initial volume ,
`V_i=4\ L` .

Final volume ,
`V_f=2\ L` .

To Find :

The change in the internal energy .

Solution :

By first law of thermodynamics :

`\Delta U=Q+W`

Here , W is work done ,
`W=-P\Delta V=-P* (V_f-V_i)`

Therefore,

`\Delta U=Q-P(V_f-V_i)`

Putting values in SI units in above equation :

`\Delta U=10 -(0.5* 101325* (2-4)* 10^(-3))\\\\\Delta U=111\ J`

Therefore , option b. is correct .

Hence , this is the required solution .