Guides
Ideal Gas Law PV=nRT — How to Use It with Examples
An ideal gas obeys PV = nRT. With R = 8.314 J/(mol·K) and consistent units (P: kPa, V: L, T: K, n: mol), substitute and solve for any unknown.
Formula & units
PV = nRT, R = 8.314 J/(mol·K). Temperature must be in kelvin (K = °C + 273.15). Since 1 kPa·L = 1 J, units are consistent with P in kPa and V in L.
Steps
- Make units consistent Temperature in K, pressure in kPa, volume in L, amount in mol.
- Write the equation PV = nRT.
- Solve for the unknown e.g. V = nRT / P, or n = PV / (RT).
- Substitute Plug in the numbers.
Worked example
Volume of 1 mol of gas at 273.15 K and 101.325 kPa?
V = nRT / P = 1 × 8.314 × 273.15 / 101.325 ≈ 22.4 L
This is the molar volume of a gas at standard conditions.
Notes & tool
The ideal gas model is an approximation; it deviates at high pressure or low temperature. Use the ideal gas calculator — fill three values, leave one blank.