Partial Pressure Guide
Partial pressure explains how each gas shares total pressure. A mixture can contain many gases. Each gas acts as if it fills the whole container alone. Dalton's law links that idea to a simple equation. The calculator uses that law, then adds practical options for real inputs.
Mole fraction is the key. It is the share of one gas compared with the total gas amount. When a gas has a larger mole fraction, its pressure share is larger. Equal temperature and volume are assumed. The gases should behave nearly ideally. That is a good model for many school, lab, and engineering problems.
The tool accepts several composition styles. You can enter moles directly. You can enter mass with molar mass. You can also enter mole fraction or volume percent. Volume percent is treated like mole percent for ideal gases. The script converts every entry into a common basis. Then it normalizes the values. This prevents small rounding errors from breaking the total.
Pressure units can confuse results. The calculator converts all pressures through pascals. You may enter atm, kPa, bar, psi, mmHg, or Pa. The final table can show another pressure unit. This helps compare textbook values, gauge readings, and lab data without manual conversion.
Wet gas mixtures need extra care. A collected gas may include water vapor. In that case, the dry gas pressure is the total pressure minus water vapor pressure. The calculator can subtract that value before computing each gas pressure. This is useful for gases collected over water.
Temperature and volume are optional. When both are entered, the page estimates total moles with the ideal gas law. It also estimates gas moles from each mole fraction. These values help check whether a measured mixture is reasonable.
Use the result as an ideal estimate. Strong intermolecular forces, high pressure, or very low temperature can cause deviation. For high accuracy, use fugacity or compressibility data. For most classroom calculations, Dalton's law gives a clear and reliable answer.
Good record keeping improves repeat work. Save the table as CSV for spreadsheets. Export the report as PDF for notes. Compare the normalized sum with your expected mixture. If it differs, check units, molar masses, wet pressure settings, and blank rows.