Question

A 19.0- L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.2 atm . Enough weight is suddenly removed from the piston to lower the external pressure to 1.6 atm . The gas then expands at constant temperature until its pressure is 1.6 atm . The change in the internal energy of a system, ΔE , for an isothermal expansion of an ideal gas is 0. Use this information in your calculations for this problem.

Part A

Find the change in the internal energy of a system for this change in state.

Express your answer using two significant figures.

Answer 1

Part A : change in the internal energy of a system for this change in state:

The internal energy is a state function in , its value depends only on the
current state of the system and it is independent of path of achieving that state.

As the process is isothermal, and as E of an ideal gas system depends only on the temperature,
The change in the internal energy of a system, ΔE , for an isothermal expansion of an ideal gas is 0.

ΔE = 0

An ideal gas is  that obeys the equation of state
PV = nRT
in which n is the amount of matter in units of moles and R is a universal constant; and (2) for which the energy U is a function of the temperature only; that is,
(dU / dP)_T = 0 and (dU /dV)_T = 0
It follows from this equation that if an ideal gas undergoes any isothermal transformation,
its energy remains fixed, i.e.  ΔE = 00.0