Ideal Gas Law Calculator
Calculate pressure, volume, temperature, or moles using the ideal gas law equation PV = nRT. Supports multiple units with step-by-step solutions and detailed explanations.
Input Variables
Ideal Gas Law Formulas
The Ideal Gas Law
Variable Definitions
Rearranged Forms
Gas Constant Values
| Units | R Value |
|---|---|
| J/(mol·K) | 8.314 |
| L·atm/(mol·K) | 0.08206 |
| L·bar/(mol·K) | 0.08314 |
About the Ideal Gas Law
The Ideal Gas Law is a fundamental equation in chemistry and physics that describes the behavior of an ideal gas under various conditions. It combines Boyle's Law, Charles's Law, and Avogadro's Law into a single, comprehensive equation that relates pressure, volume, temperature, and the amount of gas.
Key Assumptions
Point Particles
Gas molecules have negligible volume compared to the container volume.
No Intermolecular Forces
Gas molecules don't attract or repel each other.
Elastic Collisions
Collisions between molecules and container walls are perfectly elastic.
Random Motion
Gas molecules move randomly in all directions with average kinetic energy proportional to temperature.
Applications
Chemical Reactions
Calculate gas volumes and pressures in chemical reactions and stoichiometry.
Engineering
Design pressure vessels, pneumatic systems, and gas storage containers.
Environmental Science
Model atmospheric conditions and gas concentrations in environmental studies.
Limitations
The ideal gas law works best at low pressures and high temperatures. At high pressures or low temperatures, real gases deviate from ideal behavior due to molecular size and intermolecular forces. In such cases, more complex equations like the Van der Waals equation provide better accuracy.
Frequently Asked Questions
Why do I need to provide exactly 3 variables?
The ideal gas law equation PV = nRT has 4 variables. To solve for any one unknown variable, you need to know the other three. This is a fundamental requirement of algebra and physics.
Which units should I use?
You can use any combination of supported units. The calculator automatically converts between units and uses the appropriate gas constant (R) value. Common combinations include atm/L/K for chemistry and Pa/m³/K for physics applications.
Can I use Celsius or Fahrenheit for temperature?
Yes! The calculator supports Kelvin (K), Celsius (°C), Fahrenheit (°F), and Rankine (°R). However, remember that the ideal gas law requires absolute temperature, so values below absolute zero (-273.15°C or -459.67°F) will result in errors.
When does the ideal gas law not work well?
The ideal gas law is less accurate at very high pressures (above ~10 atm) or very low temperatures (near the condensation point). For real gases under extreme conditions, use equations like Van der Waals that account for molecular size and intermolecular forces.
How accurate are the calculations?
For ideal conditions, the calculations are mathematically exact. However, real gases may deviate from ideal behavior by 1-5% under normal conditions, and significantly more under extreme conditions. The calculator uses standard gas constant values with high precision.
What is STP and why is it important?
Standard Temperature and Pressure (STP) is defined as 0°C (273.15 K) and 1 atm pressure. At STP, one mole of any ideal gas occupies 22.4 liters. This is a useful reference point for many chemistry calculations and comparisons.
Can I use this for gas mixtures?
The ideal gas law applies to each gas component individually (partial pressures) and to the total mixture. For mixtures, the total pressure equals the sum of partial pressures (Dalton's Law). Use the total moles for mixture calculations.
How do I convert between different gas constant values?
The calculator automatically selects the appropriate R value based on your chosen units. Common values are R = 8.314 J/(mol·K), R = 0.08206 L·atm/(mol·K), and R = 8.314 kPa·L/(mol·K). Always ensure your units are consistent with your chosen R value.
Pro Tips
- • Always double-check your units - mismatched units are the most common source of errors
- • For temperature, remember that only absolute scales (K, °R) can be zero or negative in calculations
- • Use scientific notation for very large or very small numbers to avoid calculation errors
- • Check if your result makes physical sense - unreasonably high or low values may indicate an error