Boyle's Law

3. Boyle studied the
compressibility of gases in
1660. In his experiments he
observed "At a fixed
temperature, the volume of a
gas is inversely proportional to
the pressure exerted by the
gas." The experiment is simple:
(see figure on left).

4. Formula:
or PV=k
The equation states that product of pressure and volume is a constant
for a given mass of confined gas as long as the temperature is constant. For
comparing the same substance under two different sets of condition, the law can
be usefully expressed as
P1V1=P2V2
The equation shows that, as volume increases, the
pressure of the gas decreases in proportion. Similarly, as
volume decreases, the pressure of the gas increases.
• P is pressure of the gas
• V is volume of the gas
• k is a constant, and has units of force
times distance

5. 1. Freon-12, CCl2F2, is used in refrigeration
systems. What is the new volume (L) of
a 8.0 L sample of Freon gas initially at
550 mm Hg after its pressure is changed
to 2200 mm Hg at constant T?
Set up a data table:
Conditions 1 Conditions 2
P1 = 550 mm Hg P2 = 2200 mm Hg
V1 = 8.0 L V2 = ?

6. An animation of Boyle's Law, showing the relationship between volume and
pressure when mass and temperature are held constant.

7. Solution for Boyle’s Law V2:
P1V1 = P2V2
V2 = V1 x P1
P2
V2 = 8.0 L x 550 mm Hg = 2.0 L
2200 mm Hg
pressure ratio
decreases volume

8. 2. A sample of gaseous nitrogen in a 65.0 L automobile
air bag has a pressure of 745 mm Hg. If this sample is
transferred to a 25.0 L bag at the same temperature.
what is the pressure of the gas in the 25.0 L bag?
Solution:
It is often useful to make a table of the
information provided.
Initial conditions Final conditions
P1 = 745 mm Hg P2 = ?
V1 = 65.0 L V2 = 25.0L
Therefore,
P2 = P1V1
V2
P2 = [745 mm Hg][65.0 L]
25.0 L