Henry's Law Calculator

Calculate solubility of gases in liquids using Henry's law: C = kH * P. Find dissolved gas concentration from partial pressure or pressure from known concentration.

💨 Solutions📐 C = kH × P🧪 Chemistry

Partial pressure P (atm)

Henry constant kH (mol/L·atm)

kH values at 25C: O2=1.3x10^-3, CO2=3.4x10^-2, N2=6.5x10^-4, H2=7.8x10^-4 mol/L-atm

Please enter valid values.

Formula & Reference

Variable	Symbol	Formula	Units
Henry's Law Calculator	—	C = kH × P	mol/L

Step-by-Step Examples

Example 1

O2 in Water

Dissolved O2 at 25 C with P(O2)=0.21 atm (air). kH(O2)=1.3x10^-3 mol/L-atm.

C = kH*P = 1.3x10^-3 x 0.21 = 2.73x10^-4 mol/L
= 2.73x10^-4 x 32 x 1000 = 8.74 mg/L O2

✓ C = 2.73x10^-4 mol/L = 8.74 mg/L O2 (typical river water saturation)

Example 2

CO2 in Soda

P(CO2) = 2.5 atm in sealed bottle. kH(CO2)=3.4x10^-2 mol/L-atm.

C = 3.4x10^-2 x 2.5 = 0.085 mol/L = 85 mmol/L CO2

✓ C = 85 mmol/L dissolved CO2 in soda

Example 3

N2 Under Pressure

Scuba at 30 m: P(N2) ~ 4 atm. kH(N2)=6.5x10^-4.

C = 6.5x10^-4 x 4 = 2.6x10^-3 mol/L
4x more N2 dissolved than at surface
Rapid ascent: bubbles form (decompression sickness)

✓ C = 2.6x10^-3 mol/L N2 (dangerous if rapid ascent)

Real-World Applications

💧

Carbonated Drinks

CO2 dissolved under pressure. Opening can releases pressure: CO2 less soluble, bubbles form.

🚠

Scuba Diving Safety

N2 dissolves in blood at pressure. Must ascend slowly for dissolved N2 to leave gradually (decompression stops).

🌊

Aquatic Ecosystems

Oxygen saturation in water (8.7 mg/L at 20 C) limits aquatic life. Temperature increase reduces O2 solubility.

🏭

Industrial Chemistry

Gas absorption design (scrubbers, reactors) based on Henry constants for target gases.

Common Mistakes to Avoid

⚠️

kH depends strongly on temperature

Gas solubility decreases at higher T. O2 at 0 C: kH=2.2x10^-3. At 25 C: 1.3x10^-3. Fish kills in warm water due to low dissolved O2.

⚠️

kH units vary by convention

Some references give kH in atm-L/mol (inverse). Check units: C = kH x P or P = kH x C. Common form: C = kH x P.

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Applies to slightly soluble gases only

Henry law valid for dilute solutions. Highly soluble gases (NH3, HCl) deviate significantly from Henry law.

Frequently Asked Questions

What is Henry's Law? ▾

C = kH x P. Concentration of dissolved gas proportional to its partial pressure above solution. Higher pressure = more gas dissolves.

Why does soda fizz when opened? ▾

Sealed: P(CO2) = 2-4 atm. Open: P(CO2) ~ 0.0004 atm (atmospheric). Henry law: less CO2 dissolves, excess escapes as bubbles.

What affects Henry constant? ▾

Temperature (major: higher T decreases kH for gases). Ionic strength (salting out: dissolved salts decrease kH). Solute-solvent interactions.

Why is N2 narcosis a scuba concern? ▾

N2 dissolved in blood at high pressure crosses blood-brain barrier. At >30 m: narcosis (nitrogen narcosis). Different from decompression sickness (gas bubbles).

What is the Bunsen absorption coefficient? ▾

Alternative to kH: volume of gas (STP) dissolved per volume of liquid per atm. Related to kH: alpha = kH x 22.4 L/mol.

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Formula Explorer connections

Interpretation: This relationship connects pressure, volume, temperature, amount or phase composition for gases and volatile mixtures. Assumption: Use absolute temperature and compatible pressure-volume units. Ideal behavior weakens at high pressure, low temperature, strong intermolecular attraction or near phase change.

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