Law of Partial Pressures
Definition and meaning of Law of Partial Pressures in chemistry.
Law of Partial Pressures is the principle stating that the total pressure exerted by a mixture of gases equals the sum of the partial pressures of each individual gas component. A partial pressure is the pressure that one gas would exert if it alone occupied the entire volume at the same temperature and quantity.
In more detail
This law assumes ideal gas behavior and applies only to gases that do not interact chemically with each other. Each gas in a mixture contributes to the total pressure independently, proportional to its mole fraction. The relationship is expressed mathematically as Ptotal = P1 + P2 + P3... where P1, P2, P3 represent individual partial pressures. This principle is fundamental to understanding gas mixtures in atmospheric science, respiration, and industrial gas handling.
Key facts
| Field | Physical Chemistry |
|---|---|
| Also known as | Dalton's Law of Partial Pressures |
| Mathematical form | Ptotal = P1 + P2 + ... + Pn |
| Applies to | Non-reacting ideal gases |
Air at sea level is approximately 78% nitrogen (N2), 21% oxygen (O2), and 1% other gases. With a total atmospheric pressure of 101.3 kPa, nitrogen contributes a partial pressure of about 79 kPa, while oxygen contributes roughly 21 kPa.
Frequently asked questions
What is the difference between partial pressure and total pressure?
Total pressure is the combined pressure from all gases in a mixture. Partial pressure is the pressure contribution from one specific gas in that mixture, calculated as the mole fraction of that gas multiplied by the total pressure.
Does the Law of Partial Pressures apply to all gas mixtures?
No, it applies only to ideal gases that do not react chemically. Real gases at very high pressures or low temperatures may deviate from this law due to intermolecular forces and molecular volume effects.