Mammoth Memory

Boyle's law in use

We know that in Boyle's law

P1  V1=P2  V2

NOTE:

Temperature remains constant

Also when you sit on an exercise ball it will get smaller

Boyles law mnemonic when you sit on an exercise ball it will get smaller.

This is Boyles law.

P1 and V1 refer to the pressure and volume before you sit on the exercise ball and P2 and V2 refer to the pressure and volume after you sit on the exercise ball.

Reducing the volume of a gas increases the pressure of the gas.

Boyles law reduce the volume and increase the pressure

Push the gas into a smaller volume and the gas particles will collide more frequently with the walls. They will exert more pressure.

NOTE 1:

The standard unit used to measure pressure is Pa (Pascals)

The standard unit used to measure volume is m3 (metre cubed)

NOTE 2:

You can use other units for volume and pressure such as ml, pounds per square inch, mm of mercury (mm Hg) or atm (atmospheres) as long as you use the same units either side of the equation.

 

Examples

1. A sample of gas is at atmospheric pressure (100,000Pa) and has volume 50cm3

    Determine the new pressure if the volume is decreased to 35cm3

Reveal answer

A sample of gas is at atmospheric pressure (100,000Pa) and has volume 50cm3

Determine the new pressure if the volume is decreased to 35cm3

 

PV=constant
P1V1=P2V2

Therefore  100,000×50=P2×35

5,000,000=P2×35

Therefore  P2=5,000,00035

P2=142,857 Pa

 

2. A sample of gas has a volume of 12.0 l at a pressure of 1.00 atm. If the pressure of gas is increased to 1000 mm  Hg, what is the new volume of the gas?

Reveal answer

sample of gas has a volume of 12.0 l at a pressure of 1.00 atm. If the pressure of gas is increased to 1000 mm  Hg, what is the new volume of the gas?

P1V1=P2V2

But we must first get the two pressures in the same units of measurement

1 atm=760 mm Hg

Therefore:

P1=760
V1=12
P2=1000
V2=?

760×12=1000V2

9120=1000V2

91201000=V2

V2=9.12l

 

3. A carbon dioxide gas cylinder contains 180cm3 of gas at a pressure of 6.3×106Pa. Calculate the volume of the gas at atmospheric pressure, 1.0×105Pa

Reveal answer

A carbon dioxide gas cylinder contains 180cm3 of gas at a pressure of 6.3×106Pa. Calculate the volume of the gas at atmospheric pressure, 1.0×105Pa

P1V1=P2V2

6.3×106×180=1.0×105×V2

V2=6.3×106×1801.0×105

Therefore V2=11340 cm3