Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, temperature, or moles.
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Select which variable to solve for, then enter the other three values. The calculator uses PV = nRT with R = 8.314 J/(mol K). Results display all four variables for reference.
About Ideal Gas Law
The ideal gas law PV = nRT is one of the most important equations in chemistry and physics. It combines Boyle's law, Charles's law, and Avogadro's law into a single equation. The gas constant R = 8.314 J/(mol K) connects the macroscopic properties of pressure, volume, and temperature to the microscopic quantity of moles. While real gases deviate from ideal behavior, this law provides an excellent approximation for many practical applications in chemistry, engineering, and atmospheric science.
Frequently Asked Questions
What is the ideal gas law?
The ideal gas law PV = nRT relates pressure (P), volume (V), amount of gas in moles (n), the gas constant (R = 8.314 J/(mol K)), and absolute temperature (T). It describes the behavior of an ideal gas.
When does the ideal gas law fail?
It fails at very high pressures (molecules are close together) and very low temperatures (near condensation). Real gases deviate from ideal behavior under these conditions. The van der Waals equation provides corrections.
What value of R should I use?
R = 8.314 J/(mol K) when using pascals and cubic meters. Other common values: 0.0821 L atm/(mol K) for liters and atmospheres, or 62.36 L mmHg/(mol K).