Gas Laws: Boyle’s Law, Charles’ Law, Pressure Law and General gas Law

• Boyle’s Law
• Charles’ Law
• Pressure Law
• General gas Law

In an attempt to study the behavior of gases in relation to volume, temperature and pressure, the following conditions are investigated

• variation of volume with pressure at constant temperature, Boyle’s law
• variation  of volume with temperature at constant pressure,
  Charles law
• variation of pressure with temperature at constant volume, pressure law

Boyle’s Law

Boyle’s law states that the pressure of a fixed mass of gas varies inversely as the volume at constant temperature.

Charles’ Law

Charles law states that for a fixed mass of gas at constant pressure, the volume is proportional to its absolute temperature

Pressure Law

Pressure law states that the pressure of a fixed mass of gas at constant volume is proportional to its absolute temperature.

Absolute Zero of Temperature

When the graphs of volume – temperature or pressure – temperature are extrapolated backwards they cut the temperature axis at -273⁰C.  This temperature is called absolute zero, the temperature at which the volume of the gas theoretically becomes zero as it is being cooled. At his temperature, molecules of gas stop moving completely. This temperature is a mere assumption, as gases are known to liquefy more often than not before such a temperature is reached.

General gas Law

The general gas law is the combination of the Boyle’s, Charles and Pressure Law.

CLASSWORK 7

1. State these laws and write its mathematical expression
2. Charles’ law
3. Boyle’s law
4. A vessel is filled with a gas at a temperature 50⁰C and a pressure of 76cmHg. Calculate the final pressure if the volume of the gas is doubled while it is heated to 90⁰C

ASSIGNMENT 7

SECTION A

1. The equation P^xV^yT^z = constant is Boyle’s law if (a) x=0, y=0, z=1 (b) x=1, y=0, z=0 (c) x=1, y=1, z=0 (d) x=1, y=1, z=1 (e) x=1, y=1, z=-1
2. A column of air 10cm long is trapped in a tube at 27⁰C. What is the length of the volume at 100⁰C? (a) 12.4cm (b) 13.7cm (c) 18.5cm (d) 37.0cm (e) 100cm
3. The volume of certain quantity of gas at 27⁰C is 1200cm³. Calculate its volume at 127⁰C if the pressure remains constant.  (a) 300cm³ (b) 400cm³ (c) 1000cm³ (d) 1600cm³ (e) 250cm³
4. A fixed mass of gas of volume 600cm³ at a temperature of 27⁰C is cooled at constant pressure to a temperature of 0⁰C. What is the change in volume? (a) 54cm³ (b) 273cm³ (c) 300cm³ (d) 546cm³ (e) 600cm³
5. A mass of gas occupies 20cm³ at 5⁰C and 760mmHg pressure. What is its volume at 30⁰C and 800mmHg pressure? (a) 41.4cm³ (b) 20.7cm³ (c) 50cm³ (d) 0.4cm³ (e) 25cm³

SECTION B

1. (a) State the ideal gas equation (b) Draw graphs to show Boyle’s law and Charles law
2. (a) What is meant by absolute zero of temperature? (b) State the assumptions of the kinetic molecular theory of gases.