Question

The air within a piston equipped with a cylinder absorbs 565 J of heat and expands from an initial volume of 0.10 L to a final volume of 0.85 L against an external pressure of 1.0 atm. What is the change in internal energy of the air within the piston

Answer 1

489 J

Step-by-step explanation:

According to the first law of thermodynamics:-

`\Delta U = q + w`

Where,

U is the internal energy

q is the heat

w is the work done

From the question,

q = + 565 J (+ sign as the heat is being absorbed)

The expression for the calculation of work done is shown below as:

`w=-P* \Delta V`

Where, P is the pressure

`\Delta V` is the change in volume

From the question,

`\Delta V` = 0.85 - 0.10 L = 0.75 L

P = 1.0 atm

`w=-1.0*0.75\ atmL`

Also, 1 atmL = 101.3 J

So,

`w=-1.0*0.75* 101.3\ J=-76\ J` (work is done by the system)

So,

`\Delta U = +565\ J-76\ J = 489\ J`