Henry’s Law Gas Solubility Calculator
Easily calculate the solubility of a gas in a liquid using Henry’s Law. This tool helps you understand how gas concentration changes with pressure. Enter the values below to get started.
The pressure of the gas above the solvent.
The constant for the specific gas and solvent at a constant temperature.
Enter the molar mass (in g/mol) to convert the result to grams per liter (g/L). E.g., O₂ is ~32 g/mol.
Calculated Solubility (C)
What is Gas Solubility and Henry’s Law?
Henry’s Law is a fundamental gas law in physical chemistry, formulated by William Henry in 1803. It states that at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. In simple terms, the higher the pressure of a gas above a liquid, the more of that gas will dissolve into the liquid. This concept is crucial to calculate gas solubility using Henry’s law.
This principle is observed in many real-world scenarios. For example, carbonated beverages are bottled under high carbon dioxide pressure to dissolve more CO₂ into the drink. When you open the bottle, the pressure is released, and the solubility of CO₂ decreases, causing the gas to bubble out of the solution. This same law is critical in fields like environmental science, to understand gas exchange between the atmosphere and oceans, and in medicine, for managing dissolved gases in the bloodstream during anesthesia or diving.
The Henry’s Law Formula and Explanation
The relationship described by Henry’s Law is expressed with a simple formula:
C = kH × P
Understanding the components of this formula is key.
| Variable | Meaning | Common Unit (auto-inferred) | Typical Range |
|---|---|---|---|
| C | The concentration (solubility) of the dissolved gas. | mol/L (molarity) | Varies widely based on conditions. |
| kH | The Henry’s Law constant. This value is specific to the gas, the solvent, and the temperature. | mol/(L·atm) | From 10⁻⁴ to 10⁶ depending on the gas-solvent pair. |
| P | The partial pressure of the gas above the liquid. | Atmospheres (atm) | Usually from 0 to several atmospheres. |
Using a pressure unit converter can be helpful if your initial data is not in atmospheres.
Common Henry’s Law Constants
The Henry’s Law constant (kH) varies for each gas. Here are some approximate values for common gases dissolved in water at 25 °C:
| Gas | kH in mol/(L·atm) |
|---|---|
| Oxygen (O₂) | 0.0013 |
| Carbon Dioxide (CO₂) | 0.034 |
| Nitrogen (N₂) | 0.00061 |
| Hydrogen (H₂) | 0.00078 |
Practical Examples
Example 1: Oxygen in a Lake
Imagine you want to find the concentration of dissolved oxygen in a lake at 25 °C. The partial pressure of oxygen in the atmosphere at sea level is approximately 0.21 atm.
- Inputs:
- Partial Pressure (P): 0.21 atm
- Henry’s Law Constant (kH for O₂): 0.0013 mol/(L·atm)
- Calculation:
C = 0.0013 mol/(L·atm) × 0.21 atm = 0.000273 mol/L - Result: The solubility of oxygen in the lake water is approximately 0.000273 mol/L. This value is critical for aquatic life.
Example 2: Carbonating a Beverage
A beverage manufacturer wants to calculate gas solubility using Henry’s law for carbon dioxide. They bottle their drink under a pressure of 2.5 atm of pure CO₂ at 25 °C.
- Inputs:
- Partial Pressure (P): 2.5 atm
- Henry’s Law Constant (kH for CO₂): 0.034 mol/(L·atm)
- Calculation:
C = 0.034 mol/(L·atm) × 2.5 atm = 0.085 mol/L - Result: The concentration of dissolved CO₂ in the beverage is 0.085 mol/L. This is a much higher concentration than in the oxygen example, due to both higher pressure and a larger Henry’s Law constant.
How to Use This Gas Solubility Calculator
Follow these simple steps to use the calculator effectively:
- Enter Partial Pressure: Input the partial pressure of the gas you are analyzing. Be sure to select the correct unit (atm, Pa, kPa, etc.) from the dropdown menu.
- Enter Henry’s Law Constant: Input the specific kH value for your gas-solvent pair and temperature. Select the appropriate unit for the constant.
- Enter Molar Mass (Optional): If you want the result in grams per liter (g/L), enter the molar mass of the gas. The calculator will provide the result in both mol/L and g/L.
- Interpret the Results: The calculator instantly displays the calculated solubility. The chart below the results visualizes how solubility changes with pressure, providing a dynamic view of the relationship.
- Reset or Copy: Use the “Reset” button to clear the inputs to their default values, or use “Copy Results” to save the output to your clipboard.
Key Factors That Affect Gas Solubility
Several factors influence the solubility of a gas in a liquid. Understanding them provides a fuller context for Henry’s Law calculations.
- Pressure: As described by Henry’s Law, this is the most direct factor. Increasing partial pressure increases solubility.
- Temperature: For gases, solubility almost always decreases as temperature increases. Warmer liquids have molecules with more kinetic energy, which allows dissolved gas molecules to escape from the solution more easily. This is why a warm soda goes “flat” faster than a cold one.
- Nature of the Gas: Gases with stronger intermolecular forces or that can react with the solvent (like CO₂ forming carbonic acid in water) tend to be more soluble. This is reflected in a higher chemical equilibrium constant.
- Nature of the Solvent: The “like dissolves like” principle applies. Polar gases dissolve better in polar solvents, and nonpolar gases dissolve better in nonpolar solvents.
- Presence of Other Solutes: The presence of salts or other substances in the liquid can decrease the solubility of gases. This “salting-out” effect occurs because solvent molecules are attracted to the salt ions, leaving fewer available to interact with and dissolve the gas.
- Molar Mass of the Gas: While not a direct factor in the formula, knowing the molar mass is essential for converting between molar concentration (mol/L) and mass concentration (g/L), as you can do with our molarity calculator.
Frequently Asked Questions (FAQ)
- 1. What are the limitations of Henry’s Law?
- Henry’s Law works best for dilute solutions and at low pressures. At very high pressures, the relationship between pressure and solubility can become non-linear. It also doesn’t apply if the gas reacts chemically with the solvent in a way not accounted for by the constant.
- 2. Why does gas solubility decrease with temperature?
- Increasing the temperature adds kinetic energy to the system. This energy helps dissolved gas molecules overcome the intermolecular forces holding them in the liquid, allowing them to escape back into the gas phase, thus decreasing solubility.
- 3. How do I find the correct Henry’s Law constant?
- The constant is specific to the gas, solvent, and temperature. You’ll typically find it in chemistry handbooks, scientific literature, or online databases. Our table provides a few common examples for water at 25 °C.
- 4. Can this calculator be used for any liquid, not just water?
- Yes, as long as you have the correct Henry’s Law constant (kH) for that specific gas-solvent combination. The constant for oxygen in ethanol, for example, is different from the constant for oxygen in water.
- 5. What is the difference between Henry’s Law and Dalton’s Law?
- Dalton’s Law describes the total pressure of a gas mixture as the sum of the partial pressures of its individual components. Henry’s Law describes the solubility of one of those components in a liquid. They are often used together; for example, using a Dalton’s Law partial pressure calculator to find the ‘P’ value to then use in the Henry’s Law equation.
- 6. How do I handle unit conversions for the Henry’s Law constant?
- Constants can come in many units. Our calculator provides options for the most common ones. If your constant has different units (e.g., involving Pascals or mole fractions), you will need to convert it to one of the supported units before entering it.
- 7. What does a “unitless” Henry’s constant mean?
- Sometimes the constant is given as a dimensionless value, which typically relates the mole fraction of the gas in the liquid phase to the mole fraction in the gas phase. This is a different formulation and requires a different calculation approach not used in this specific calculator.
- 8. Can I calculate gas solubility using Henry’s law for a gas mixture?
- Yes. You apply Henry’s Law to each gas independently. You need the partial pressure of each gas in the mixture and the specific Henry’s Law constant for each gas.
Related Tools and Internal Resources
Explore these related calculators and articles for a deeper understanding of gas laws and chemical principles:
- Ideal Gas Law Calculator: Explore the relationship between pressure, volume, temperature, and moles of a gas.
- Dalton’s Law Partial Pressure Calculator: Calculate the partial pressures of gases in a mixture.
- Understanding Chemical Equilibrium: A guide to the principles that govern reversible reactions, including dissolution.
- Molarity Calculator: Convert between mass, volume, and molar concentration.
- Solution Concentration Units: An overview of different ways to express the concentration of a solute.
- Pressure Unit Converter: Easily convert between different units of pressure.