Ideal Gas Law formula:
story, analogy and memory trick
The Ideal Gas Law formula is PV = nRT. For an ideal gas, pressure times volume equals the number of moles times the gas constant times the absolute temperature.
The Ideal Gas Law formula
- Ppressure of the gas
- Vvolume of the gas
- namount of gas, in moles
- Runiversal gas constant
- Tabsolute temperature, in kelvin
The story
Think of a sealed flask as a classroom of gas particles. More students (n) or a hotter, more excited room (T) means harder bumping into the walls, so the pressure P rises. Give them a bigger room V and the bumping eases.
Real-life analogy
Think of a bicycle tyre. Pump in more air (n) and the pressure P rises. Leave it in the hot sun (T) and it gets harder. The tyre's fixed size is V.
Memory trick
Say the letters in order: P V n R T, or use the line 'Please Visit Nandu's Restaurant Today'.
Exam tip
Temperature must be in kelvin (K = °C + 273). Pick the value of R to match your units: 0.0821 L·atm/(mol·K) or 8.314 J/(mol·K).
Questions about Ideal Gas Law
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More Chemistry formulas
Boyle's Law
P₁V₁ = P₂V₂
At constant temperature, the pressure of a fixed amount of gas is inversely proportional to its volume, so P times V stays constant.
Read the storyMolarity
M = moles of solute ÷ litres of solution
Molarity tells you how many moles of solute are dissolved in each litre of solution.
Read the storypH
pH = −log₁₀[H⁺]
pH is the negative base-10 logarithm of the hydrogen-ion concentration, so a lower pH means a more acidic solution.
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