Dalton’s law of partial pressures

Definition

Dalton's law of partial pressures states that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas. Each gas in a mixture behaves independently and contributes to the total pressure in proportion to its mole fraction.

5 Must Know Facts For Your Next Test

1. The formula for Dalton's law is $P_{total} = P_1 + P_2 + ... + P_n$, where $P_1, P_2, ..., P_n$ are the partial pressures of each gas.
2. Partial pressure is calculated using $P_i = X_i \cdot P_{total}$, where $X_i$ is the mole fraction of the gas.
3. This law applies only to ideal gases or gases that obey ideal gas behavior under certain conditions.
4. In mixtures, each gas exerts pressure as if it were alone in the container, regardless of other gases present.
5. Dalton's law can be used with the ideal gas law equation ($PV=nRT$) to find various properties like volume, temperature, or number of moles.

Review Questions

• What is Dalton's law of partial pressures and how is it mathematically expressed?
• How do you calculate the partial pressure of a single gas in a mixture?
• Under what conditions does Dalton's law hold true?

Related terms

Ideal Gas Law:

A fundamental equation describing the relationship between pressure (P), volume (V), number of moles (n), temperature (T), and the gas constant (R): $PV = nRT$.

Mole Fraction:

The ratio of the number of moles of a component to the total number of moles in a mixture: $X_i = \frac{n_i}{n_{total}}$.

Partial Pressure:

The pressure exerted by an individual gas within a mixture, calculated as $P_i = X_i \cdot P_{total}$.