Question

A gas is compressed at a constant pressure of 0.8atm from 9.00L to 2.0 L. In the process, 400J of energy leaves the gas by heat. (a) What is the work done on the gas? (b) What is the change in its internal energy?

Answer 1

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Answer 2

Concept:

Work is defined as the energy that is applied to or removed from an object by applying force along a displacement.

Given:

The pressure of compressed gas is $0.8$ atm from $9L$ to $2L$.

The energy flow as heat is $400J$.

Find:

The work done on the gas and the change in its internal energy.

Solution:

Energy as heat, $Q=400J$

The pressure, $P_{ext}=0.8$

Volume, $V_1=9L$ and $V_2=2L$

The work done is:

$W=-P_{ext}(V_2-V_1)\\W=-0.8(2-9)\\W=5.6$in liter per atom.

Now, $1L-atm=101.33J$

$W=5.6\times101.33\\W=567.48J$

Using the first law of thermodynamics,

$\Delta U=Q+W\\\Delta U=-400J+567.48=167.48J$

The work done on the gas is $567.48J$ and the change in its internal energy is $167.48J$.

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