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Calculating Pressure Using the Ideal Gas Law Equation

The problem is this....

A gas with a volume of 4.0L is contained is a closed container. Indicate the changes in pressure when the volume undergoes the following changes at a constant temperature.

A. The vloume is compressed to 2 L.
B. The vloume is allowed to expand to 2 L.
C. The volume is copmressed to .40 L.
(This is part of a study guide. The answers at the end are as follows:
A. The pressure doubles.
B. The pressure falls to one third the initial pressure.
C. The pressure increases to ten times the original pressure.

How do I know this, and how do I figure out these answers without knowing the pressure? I don't know how to set up this problem.

Solution Preview


First of all we have to find out the properties of the gas to use the correct equation.
Here no interaction between the particles are considered.
So we have an ideal gas.
The equation we use then is the ideal gas law equation:

p * V = R * T

with R as the ideal gas law ...

Solution Summary

Here it is described how the ideal gas law equation can be used to calculate changes of pressure of an ideal gas when its volume change. First it is explained the expression 'ideal gas' and then a step-by-step explanation of the solution.