1.2.3

# The Ideal Gas Equation

Test yourself

## The Ideal Gas Equation

Most gases obey a simple law known as the ideal gas equation. This describes the relationship between the pressure, volume and temperature of a gas.

### The ideal gas equation

• The ideal gas equation is:
• Pressure × volume = number of moles × gas constant × temperature
• pV = nRT
• This equation can be used to calculate any variable in the equation, as long as you know the other three variables.
• p, V, n, and T are the variables.
• R is a constant - its value is always 8.314.

### Importance of units

• When using the ideal gas law, it is important to make sure you are using only SI units:
• Pressure must be in Pascals (Pa).
• Volume must be in cubic metres (m3).
• Temperature must be in Kelvin (K).
• These units are the scientific standard - they are all related and allow for easily understood numbers.
• Using different units will give you the wrong answer!

### An example

• The pressure of 1 mole of a gas is 100 kPa (1x105 Pa) at a temperature of 298 K. What is its volume?
• pV = nRT
• V = nRT ÷ p
• V = 1 × 8.314 × 298 K ÷ 105 Pa
• V = 0.0248 m3