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Molar Calculations of Gases

We can also calculate the number of moles of a gas. It is difficult to measure the mass or the concentration of a gas so we must use another equation.

Avogadro's Law

Avogadro's Law

  • The equation is based upon Avogadro's Law:
    • Avogadro's Law says that at the same temperature and pressure, one mole of two different gases will be the same volume.
  • So, regardless of what the gas is, one mole of a gas will always be a particular volume at a specific temperature and pressure.
Room temperature and pressure

Room temperature and pressure

  • At room temperature and pressure, 24 dm3 is the volume taken up by one mole of any gas.
The equation for moles in a gas

The equation for moles in a gas

  • This leads to the equation:
    • Number of moles of a gas = volume of the gas ÷ 24
  • This equation is only true if:
    • The volume is measured in dm3.
    • The gas is at room temperature and pressure.
The equation for volume of a gas

The equation for volume of a gas

  • Another form of this equation gives the equation
    • Volume of a gas = moles of the gas × 24
  • This equation volume calculated:
    • Is in dm3.
    • Is correct at room temperature and pressure.
Converting the equation

Converting the equation

  • A useful conversion for this equation is:
    • 1 m3 = 1,000 dm3
  • Alternatively, we can use the converted equation:
    • Number of moles of a gas = volume of the gas ÷ 24,000
    • Volume of a gas = number of moles of the gas × 24,000
    • This is true for the volume in cm3.
Jump to other topics
1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.2

Atomic Structure

1.3

Chemical Bonding

1.4

States of Matter

1.5

Chemical Energetics

1.6

Electrochemistry

1.7

Equilibria

1.8

Partition Coefficient

1.9

Reaction Kinetics

2

Inorganic Chemistry

3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.2

Hydrocarbons

3.3

Halogen Derivatives

3.4

Hydroxy Compounds

3.5

Carbonyl Compounds

3.6

Carboxylic Acids & Derivatives

3.7

Nitrogen Compounds

3.8

Polymerisation

3.9

Analytical Techniques

3.10

Organic Synthesis

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