Gas Laws

# Gas Laws

The fundamental laws of gases or volumetric laws are the following: gas laws chemistry

• Avogadro’s Law: gas laws chemistry
• Avogadro discovers in 1811 that at constant pressure and temperature, the same amount of gas has the same volume regardless of the chemical element that forms it.
• The volume ( V ) is directly proportional to the amount of gas particles ( n ) independent of the chemical element that forms the gas
• Therefore: 1 / 1 = 2 / 2
• Which has the consequence that:
• If you increase the amount of gas, you increase the volume
• If the amount of gas decreases, the volume decreases
• Boyle’s Law:
• Boyle discovered in 1662 l to pressure exerted by a gas is inversely proportional to its volume at constant temperature and gas amount: P = k / V → P · V = k (k is a constant). gas laws chemistry
• Therefore: 1 · 1 = 2 · 2
• Which has the consequence that: gas laws chemistry
• If the pressure increases the volume decreases
• If the pressure decreases the volume increases
• Note : It is also called the Boyle-Mariotte Law as he discovered it independently in 1676 .
• Charles Law: gas laws chemistry
• Charles discovered in 1787 and l volume of gas is directly proportional to the temperature at constant pressure: V = k · T (k is a constant).
• Therefore: 1 / 1 = 2 / 2
• Which has the consequence that:
• If the temperature increases the volume increases
• If the temperature decreases the volume decreases
• Note : Also called Charles and Gay-Lussac’s Law.
• Gay Law – Lussac:
• Gay-Lussac discovers in 1802 that the pressure of the gas is directly proportional to its temperature at constant volume: P = k · T (k is a constant).
• Therefore: 1 / 1 = 2 / 2
• Which has the consequence that: gas laws chemistry
• If the temperature increases the pressure increases
• If the temperature decreases the pressure decreases
• Ideal Gas Law: gas laws chemistry
• Ideal gases have the following properties:
• Gas molecules move at high speeds in a linear but disorderly manner
• The speed of the gas molecules is proportional to their absolute temperature
• The gas molecules exert sustained pressure on the walls of the container that contains it.
• The collisions between the gas molecules are elastic so they do not lose kinetic energy
• The attraction / repulsion between gas molecules is negligible gas laws chemistry
• For these ideal gases the following law is fulfilled:

P · V = n · R · T

• Where n are the moles of the gas and R the universal constant of the ideal gases. gas laws chemistry
• General Gas Law: gas laws chemistry
• The General Gas Law consists of the union of the following laws:
• Boyle ‘s law: 1 · 1 2 · 2
• Gay-Lussac’s Law: 1 / 1 2 / 2
• Charles Law: 1 / 1 2 / 2
• All of them are condensed into the following formula:

1 · 1 1 2 · 2 2

• Graham’s Law:
• Formulated by Graham discovered in 1829:
• The rates of effusion (exit through pores) and diffusion (expansion until occupying the volume of the container) of gases are inversely proportional to the square root of their molar masses: gas laws chemistry

1 2 = ( 2 1 ) -1/2

• where: 1 , 2 are the diffusion / effusion masses of the gas and 2, M 1 are the molar masses
• Dalton’s Law:
• Formulated by Dalton in 1801.
• The total pressure of a gas mixture is equal to the sum of the pressures exerted by each of the gases that compose it.
• The pressure exerted by each gas in the mixture is called Partial Pressure. Therefore this law can be expressed as:

Total 1 + 2 + … + n

• Where 1 , 2 , …, n are the partial pressures of each of the gases in the mixture. gas laws chemistry
• Henry’s Law:
• Made by Henry in 1803.
• The amount of gas dissolved in a liquid at constant temperature is proportional to the partial pressure of the gas above the liquid.
• This law is summarized in the following equation:

p H · c

• Where: p : partial pressure of the gas, c : concentration of the gas and H : Henry’s constant. gas laws chemistry