Ideal Gas Law Calculator (PV=nRT)

Ideal Gas Law Calculator (PV=nRT)

What is the Ideal Gas Law?

The Ideal Gas Law is a fundamental equation in chemistry and physics that describes the behavior of most gases under moderate conditions. The law is stated as:

PV = nRT

Where:
• P = Pressure of the gas
• V = Volume of the gas
• n = Number of moles of the gas
• R = The Ideal Gas Constant
• T = Absolute temperature of the gas (in Kelvin)

This equation relates all four major properties of a gas. If you know any three of these properties, you can use this calculator to solve for the fourth.

Frequently Asked Questions

What is the Gas Constant (R)?

The Ideal Gas Constant, R, is a proportionality constant that makes the equation true. Its value changes depending on the units you use for Pressure and Volume. This calculator automatically selects the correct value of R based on your chosen units to ensure the calculation is always correct. The most common values are:
• 0.08206 L·atm/(mol·K)
• 8.314 kPa·L/(mol·K)
• 62.36 L·mmHg/(mol·K)
• 8.314 J/(mol·K) or Pa·m³/(mol·K)

When does the Ideal Gas Law fail?

The Ideal Gas Law assumes that gas particles themselves have no volume and do not attract or repel each other. This is a good approximation under normal conditions (low pressure, high temperature). However, the law becomes less accurate at:
High Pressures: The volume of the gas particles becomes significant compared to the container volume.
Low Temperatures: The attractive forces between particles (which are ignored by the law) become strong enough to cause the gas to condense into a liquid.

Why must I use Kelvin for temperature?

The Ideal Gas Law is based on a proportional relationship. For example, if you double the absolute temperature (in Kelvin), you double the pressure (if V and n are constant). This relationship doesn't work with Celsius or Fahrenheit. For example, 20°C is not "double" 10°C in terms of kinetic energy. The Kelvin scale starts at absolute zero (0 K = -273.15 °C), the point at which all particle motion theoretically stops. This calculator automatically converts °C and °F to Kelvin before calculating.