How To Calculate Partial Pressure With Moles

Dalton's Law of Partial Pressures:

\[ P_i = \frac{n_i}{n_{total}} \times P_{total} \]

Partial Pressure of Gas i (P_i):

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1. What Is Dalton's Law of Partial Pressures?

Dalton's Law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of individual gases. The partial pressure of each gas is proportional to its mole fraction in the mixture.

2. How Does the Calculator Work?

The calculator uses Dalton's Law equation:

\[ P_i = \frac{n_i}{n_{total}} \times P_{total} \]

Where:

\( P_i \) — Partial pressure of gas i (Pa)
\( n_i \) — Moles of gas i (moles)
\( n_{total} \) — Total moles of gas mixture (moles)
\( P_{total} \) — Total pressure of gas mixture (Pa)

Explanation: The equation calculates the pressure that each individual gas would exert if it alone occupied the entire volume of the mixture at the same temperature.

3. Importance of Partial Pressure Calculation

Details: Partial pressure calculations are essential in gas laws, respiratory physiology, industrial gas processes, scuba diving, and atmospheric science. They help predict gas behavior in mixtures and are fundamental to understanding gas exchange in biological systems.

4. Using the Calculator

Tips: Enter moles of the specific gas, total moles of the gas mixture, and total pressure. All values must be positive, and moles of individual gas cannot exceed total moles. Ensure consistent units throughout the calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the physical significance of partial pressure?
A: Partial pressure represents the pressure that a gas would exert if it alone occupied the entire volume of the mixture at the same temperature.

Q2: Can this equation be used for reacting gases?
A: No, Dalton's Law applies only to mixtures of non-reacting gases. For reacting gases, the composition changes and the law doesn't directly apply.

Q3: What units should I use for pressure?
A: While Pascals (Pa) are used here, you can use any pressure unit (atm, mmHg, bar) as long as you maintain consistency throughout the calculation.

Q4: How does temperature affect partial pressure?
A: Temperature affects the total pressure according to the ideal gas law, but the mole fractions and thus the partial pressure proportions remain constant at constant volume.

Q5: What are common applications of partial pressure calculations?
A: Respiratory gas exchange, industrial gas separation processes, scuba diving decompression calculations, and atmospheric science studies.