The Ideal Gas Equation
Chemistry: AQA A Level, topic 1.2.3
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
Test yourself on The Ideal Gas Equation
What is the ideal gas equation?
Which is true of the ideal gas equation?
Which of these is NOT a variable in the ideal gas equation?