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

Answer:

489 J

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:

$w=-P\times \Delta V$

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

$w=-1.0\times0.75\ atmL$

Also, 1 atmL = 101.3 J

So,

$w=-1.0\times0.75\times 101.3\ J=-76\ J$ (work is done by the system)

So,

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