Question

A sample of gas is contained in an expandable balloon. 10 KJ of heat is transferred to the gas which causes the balloon to expand at constant pressure. If the internal energy of the gas does not change during this process, calculate the work done and the change in volume ( in L) of the balloon. ( the pressure of the surroundings is 1030 mBar). ( 1 J= 1 Pa m^3 )

Answer 1

Since the internal energy does not change, this means that the temperature remains constant and the process is isothermal.

Hence all the heat supplied to the gas is used against expansion.

So, work done by the gas in the expanding balloon = 10 kJ = 10000 J

Also, we make use of the relation at isothermal conditions:

Work done, W = P*dV

Here, P = external pressure = 1030 mbar = 1.03 bar = 103000 Pa

Putting values:

10000 = 103000*dV

So,

dV = 10000/103000 = 0.0971 m³ = 97.1 L

Hope this helps !