Calculation Results
| Gas | Partial Pressure | Mole Fraction | Composition | Moles | Molar Mass | Partial Volume |
|---|
Step-by-step solution
Formula Used
Dalton's law adds the absolute partial pressures of nonreacting gases. Mole fractions describe each gas share of the mixture. Ideal behavior gives the closest results at moderate pressures.
How to Use This Calculator
- Select the calculation mode and pressure unit.
- Enter total pressure, temperature, volume, or advanced values when required.
- Add each gas and provide partial pressure, moles, mole fraction, or percentage.
- Choose automatic water correction for gas collected over water.
- Press Calculate Gas Mixture to view results, checks, charts, and steps.
- Copy, print, share, or export the completed calculation.
Example Gas Mixture Data
| Gas | Partial pressure | Mole fraction | Composition | Molar mass |
|---|---|---|---|---|
| Nitrogen | 79.0 kPa | 0.780 | 78.0% | 28.0134 g/mol |
| Oxygen | 21.2 kPa | 0.209 | 20.9% | 31.9988 g/mol |
| Argon | 0.94 kPa | 0.0093 | 0.93% | 39.948 g/mol |
| Carbon dioxide | 0.04 kPa | 0.0004 | 0.04% | 44.0095 g/mol |
Understanding Dalton's Law for Gas Mixtures
Dalton's law states that a nonreacting gas mixture has one total pressure. Each gas creates a partial pressure as though it occupied the container alone. Adding those partial pressures gives the measured absolute pressure.
Mole fraction links composition directly with pressure for an ideal mixture. A gas holding thirty percent of the moles contributes thirty percent of total pressure. This relationship makes composition calculations fast and transparent.
Gas collected over water also contains water vapor. The water contribution depends mainly on temperature and saturation. Subtracting it reveals the dry gas pressure used in many laboratory calculations.
The ideal gas equation can generate partial pressures from moles. Temperature must be absolute, and volume must use compatible units. The compressibility factor adds a simple real-gas adjustment when needed.
Mixture molar mass is a mole-fraction-weighted average. It supports density estimates and several engineering calculations. Accurate component molar masses improve the final mixture properties.
Gauge pressure needs careful treatment because Dalton's law uses absolute pressure. This calculator converts the entered total gauge pressure using local atmospheric pressure. Individual partial pressures should normally be entered as absolute values.
Charts help compare gas contributions without replacing the numerical table. The pie chart emphasizes composition, while bars compare pressure magnitudes. Export tools preserve results for reports and quality records.
Real gas behavior grows important at high pressure or low temperature. A single compressibility factor is only an approximation for complex mixtures. Detailed process design may require an equation of state.
Always confirm units before interpreting a result. Check fraction totals, pressure limits, and temperature conversions. Careful inputs produce reliable gas-mixture calculations for practical laboratory work.
Frequently Asked Questions
What is Dalton's law?
It states that total pressure equals the sum of component partial pressures for a nonreacting gas mixture.
Must pressures be absolute?
Yes. Dalton's law is based on absolute pressure. Gauge pressure must be converted before composition calculations.
What is partial pressure?
Partial pressure is the pressure one gas contributes to the total mixture pressure.
How is mole fraction calculated?
Divide a gas partial pressure by the absolute total pressure, or divide its moles by total moles.
Why subtract water-vapor pressure?
Gas collected over water contains both the target gas and water vapor. Subtraction isolates dry gas pressure.
Can percentages replace mole fractions?
Yes. Divide each percentage by one hundred before applying the partial-pressure formula.
What does compressibility factor mean?
Z adjusts the ideal gas equation for approximate real-gas behavior. Z equals one for an ideal gas.
Can the calculator estimate gas density?
Yes. It uses total absolute pressure, mixture molar mass, temperature, gas constant, and compressibility factor.
What happens when fractions do not total one?
The calculator shows a warning. It can still calculate, but the mixture input should be reviewed.
Does Dalton's law apply to reacting gases?
Not directly. Chemical reactions change component amounts, so equilibrium or reaction calculations may be required first.
Can I export the results?
Yes. Results can be copied, printed, shared, downloaded as CSV, or saved as a PDF report.
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