The ideal gas equation is a formula that expresses the law of the relationship between pressure, volume, number, and temperature of ideal gases.

With this simple equation, you can calculate the remaining variables you don’t know. In mathematics, this process is expressed as ‘solving an equation.’

The equation has the following form:

Pressure × Volume ∝ Number of gas molecules × Temperature

The ‘∝’ symbol indicates that this equation is proportional. You can use a ‘proportionality constant’ to convert a proportional expression into an equation. The proportionality constant used here is known as the ideal gas constant (R).

The equation below applies units commonly used in chemistry. Be careful about using absolute temperature (K) as the temperature unit.

Clicking the ‘Solve’ button will find the solution for the variable.

P | V | = | n | R | T | |||
---|---|---|---|---|---|---|---|---|

× | = | × | 0.082 | × | ||||

atm | L | mol | L⋅atm/K⋅mol | K (0℃) | ||||

The equation below applies units commonly used in physics. Be careful about using absolute temperature (K) as the temperature unit.

Clicking the ‘Solve’ button will find the solution for the variable.

P | V | = | n | R | T | |||
---|---|---|---|---|---|---|---|---|

× | = | × | 8.314 | × | ||||

Pa, N/m² | m³ | mol | J/K⋅mol | K (0℃) | ||||

## Conditions for ideal gas

The ideal gas is a hypothetical gas that follows the ideal gas law. An ideal gas must satisfy the following conditions:

- Gas molecules are so small and identical that they are indistinguishable.
- Gas molecules are assumed to be very small, so the volume of the molecules themselves is ignored.
- The only interaction between gas molecules is physical collision. Molecules have perfectly elastic collisions no matter where they collide.
- The motion of molecules follows Newton’s laws of motion.
- Molecules move randomly. In other words, the motion of molecules can only be described statistically, and individual motion is not covered.

Real gas particles have volume and interact with each other. Therefore, strictly speaking, no gas can be an ideal gas.

However, at very high temperatures and low pressures, most gases have properties similar to ideal gas.