Gas Law Calculator

Calculate pressure, volume, temperature, and moles using ideal gas law and gas law relationships with our comprehensive Gas Law Calculator.

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Advanced Gas Law Calculator

Calculate gas properties using ideal gas law, combined gas laws, and real gas equations with comprehensive analysis and visual representations.

Gas Law Type

Calculate which property?

moles (mol)

Results & Analysis

⚗️
Enter values and click calculate to see comprehensive gas analysis

Gas Constants

R = 0.08206 L·atm/(mol·K)
R = 8.314 J/(mol·K)
R = 1.987 cal/(mol·K)
STP: 273.15 K, 1 atm
Molar Volume (STP): 22.4 L/mol

Pressure Conversions

1 atm = 101,325 Pa
1 atm = 760 mmHg
1 atm = 760 Torr
1 atm = 1.01325 bar
1 atm = 14.696 psi

Temperature Conversions

K = °C + 273.15
°C = (°F - 32) × 5/9
°F = °C × 9/5 + 32
Absolute Zero: 0 K = -273.15°C
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About the Gas Law Calculator

Our advanced gas law calculator is a comprehensive tool that handles all major gas law relationships, from simple ideal gas calculations to complex real gas equations. It supports the ideal gas law (PV = nRT), individual gas laws (Boyle's, Charles's, Gay-Lussac's), combined gas law, and van der Waals equation for real gases.

This calculator provides automatic unit conversions, comparative analysis between ideal and real gas behavior, STP calculations, and detailed step-by-step solutions - making it perfect for students, researchers, and professionals working with gases.

Gas Law Formulas

Ideal Gas Law

\[ PV = nRT \]
Where P = pressure, V = volume, n = moles, R = gas constant, T = temperature

Combined Gas Law

\[ \frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2} \]
Relates initial and final states of a gas sample

Boyle's Law

\[ P_1V_1 = P_2V_2 \]
At constant temperature and amount

Charles's Law

\[ \frac{V_1}{T_1} = \frac{V_2}{T_2} \]
At constant pressure and amount

Van der Waals Equation

\[ \left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT \]
For real gases with intermolecular forces

Gay-Lussac's Law

\[ \frac{P_1}{T_1} = \frac{P_2}{T_2} \]
At constant volume and amount

How to Use This Calculator

Step-by-Step Guide

  1. Select Gas Law: Choose the appropriate gas law for your problem
  2. Choose Calculation: Select which property you want to calculate
  3. Enter Known Values: Input the given quantities with their units
  4. Unit Selection: Use dropdown menus for automatic unit conversion
  5. Calculate: Click calculate to get comprehensive results
  6. Analyze Results: Review unit conversions, STP properties, and comparisons

Pro Tips

  • Always use absolute temperature (Kelvin) for accurate calculations
  • For real gas calculations, select the appropriate gas or enter custom constants
  • Use STP conditions (273.15 K, 1 atm) as reference points
  • Compare ideal vs real gas results to understand deviations
  • Check unit conversions to verify your results
  • Use the gas constant table for different unit systems

Worked Examples

Example 1: Ideal Gas Law - Find Pressure

Given:

  • • Volume (V): 2.5 L
  • • Temperature (T): 25°C = 298.15 K
  • • Amount (n): 0.5 mol
  • • Gas constant (R): 0.08206 L·atm/(mol·K)

Solution:

Using PV = nRT
P = nRT/V
P = (0.5 × 0.08206 × 298.15) / 2.5
P = 4.88 atm

Example 2: Combined Gas Law

Given:

  • • Initial: P₁ = 1.0 atm, V₁ = 3.0 L, T₁ = 300 K
  • • Final: P₂ = 2.0 atm, T₂ = 400 K
  • • Find: V₂

Solution:

Using (P₁V₁)/T₁ = (P₂V₂)/T₂
V₂ = (P₁V₁T₂)/(P₂T₁)
V₂ = (1.0 × 3.0 × 400)/(2.0 × 300)
V₂ = 2.0 L

Example 3: Real Gas (Van der Waals)

Given (CO₂):

  • • Volume (V): 1.0 L
  • • Temperature (T): 300 K
  • • Amount (n): 1.0 mol
  • • a = 3.640 L²·atm/mol²
  • • b = 0.04267 L/mol

Solution:

Using (P + an²/V²)(V - nb) = nRT
P = nRT/(V - nb) - an²/V²
P = (1×0.08206×300)/(1-0.04267) - 3.640/1²
P = 21.02 atm
(vs 24.62 atm for ideal gas)

Understanding Your Results

Gas Law Applications

Ideal Gas Law
Best for gases at low pressure and high temperature
Boyle's Law
Pressure-volume relationship at constant temperature
Charles's Law
Volume-temperature relationship at constant pressure
Real Gas Equations
Account for molecular size and intermolecular forces

When to Use Each Law

Ideal Gas Law
P < 10 atm, T > 273 K, non-polar gases
Combined Gas Law
Comparing different states of the same gas sample
Van der Waals
High pressure, low temperature, polar gases

Frequently Asked Questions

When should I use the ideal gas law vs real gas equations?

Use ideal gas law for low pressures (<10 atm) and high temperatures (>273 K). Use real gas equations for high pressures, low temperatures, or when high accuracy is needed.

Why must temperature be in Kelvin?

Gas laws are based on absolute temperature scale. Celsius and Fahrenheit have arbitrary zero points, while Kelvin starts at absolute zero where molecular motion ceases.

What are van der Waals constants 'a' and 'b'?

'a' corrects for intermolecular attractions (larger for polar molecules), 'b' corrects for molecular volume (larger for bigger molecules).

How accurate are these calculations?

Ideal gas law: ±5% under normal conditions. Van der Waals: ±2% for most gases. For extreme conditions, use equation of state specific to the gas.

Applications & Use Cases

🎓

Education

  • • Chemistry coursework
  • • Physics problems
  • • Laboratory calculations
  • • Exam preparation
🏭

Industrial

  • • Process design
  • • Pressure vessel sizing
  • • Gas storage calculations
  • • Safety assessments
🔬

Research

  • • Gas chromatography
  • • Reaction kinetics
  • • Atmospheric studies
  • • Material science

Limitations & Considerations

Important Notes

  • Ideal Gas Limitations: Fails at high pressure (>10 atm) and low temperature (<273 K)
  • Real Gas Accuracy: Van der Waals equation has ~2% error; more complex equations needed for extreme conditions
  • Temperature Scale: Always use absolute temperature (Kelvin) for accurate calculations
  • Gas Mixtures: These calculations assume pure gases; use partial pressure laws for mixtures
  • Phase Changes: Gas laws don't apply during condensation or sublimation
  • Chemical Reactions: Calculations assume no chemical reactions occur
  • Significant Figures: Results shown with high precision; round according to input data quality
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