How To Calculate Partial Pressure

Dalton's Law Formula:

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

Partial Pressure (P_i):

Unit Converter ▲

Unit Converter ▼

From:	To:

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 the individual gases. The partial pressure of a gas is the pressure that gas would exert if it alone occupied the entire volume.

2. How Does the Calculator Work?

The calculator uses Dalton's Law formula:

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

Where:

\( P_i \) — Partial pressure of the gas (Pa)
\( n_i \) — Moles of the specific gas (mol)
\( n_{total} \) — Total moles of all gases in the mixture (mol)
\( P_{total} \) — Total pressure of the gas mixture (Pa)

Explanation: The formula calculates the portion of total pressure contributed by a specific gas based on its mole fraction in the mixture.

3. Importance of Partial Pressure Calculation

Details: Partial pressure calculations are essential in various fields including respiratory physiology, scuba diving, chemical engineering, and atmospheric science. They help determine gas exchange rates, solubility, and reaction equilibria.

4. Using the Calculator

Tips: Enter the moles of the specific gas, total moles of all gases, and the total pressure of the mixture. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What units should I use for pressure?
A: While the calculator uses Pascals (Pa), you can use any pressure unit as long as you're consistent. Common alternatives include atm, mmHg, or bar.

Q2: Does Dalton's Law apply to reacting gases?
A: Dalton's Law applies specifically to mixtures of non-reacting gases. For reacting gases, the partial pressures may change as reactions occur.

Q3: How does temperature affect partial pressure?
A: Temperature affects the total pressure of a gas mixture (via the ideal gas law), which in turn affects all partial pressures proportionally.

Q4: Can I calculate partial pressure using volume fraction?
A: For ideal gases at the same temperature and pressure, volume fraction equals mole fraction, so you can use volume ratios instead of mole ratios.

Q5: What is the relationship between partial pressure and concentration?
A: For ideal gases, partial pressure is directly proportional to concentration (P_i = (n_i/V)RT), where concentration is n_i/V.