Name: gas mixtures and their partial pressures
Uploaded: 2023-09-18T17:11:17.000Z
Duration: 1 min 11 s
Channel: JoVE

Considérons un gaz à l’intérieur d’un récipient. La pression exercée par le gaz est la somme des forces exercées en raison des collisions moléculaires entre ses molécules et la surface environnante.
Un gaz avec de nombreuses molécules exerce une pression plus élevée qu’un gaz avec un plus petit nombre de molécules dans le même récipient. Ainsi, la pression du composant individuel est appelée sa pression partielle.
Considérons un mélange de gaz idéaux dans un récipient à l’équilibre thermique. La pression totale à l’intérieur du récipient est égale à la somme des pressions partielles de ses composants. Cette observation est connue sous le nom de loi de Dalton sur les pressions partielles.
En rappelant l’équation des gaz parfaits et en substituant les pressions partielles des gaz individuels, la pression totale peut être déterminée.
La pression partielle d’une vapeur qui est en équilibre avec la phase liquide de la même substance est appelée pression de vapeur.
Le rapport entre la pression partielle de la vapeur d’eau et la pression de vapeur de l’eau à une température donnée est connu sous le nom d’humidité relative.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web], p. 37 et 38. Récupéré de <a href="https://openstax.org/books/university-physics-volume-2/pages/2-2-pressure-temperature-and-rms-speed">https://openstax.org/books/university-physics-volume-2/pages/2-2-pressure-temperature-and-rms-speed</a></li>
</ol>

la loi des pressions partielles de dalton

Dalton's Law of Partial Pressure

La pression partielle d'un gaz est une mesure de l'activité thermodynamique des molécules du gaz. La pression qu'un gaz créerait s'il occupait le volume total disponible est appelée la pression partielle du gaz. Si deux ou plus de gaz sont mélangés dans un contenant, les molécules se déplacent aléatoirement et entrent en collision les unes avec les autres, ce qui les amène à atteindre un équilibre thermique. Lorsque les gaz ont la même température, leurs molécules ont la même énergie cinétique moyenne. Ainsi, chaque gaz obéit séparément à la loi des gaz parfaits et exerce la même pression individuellement sur les parois du contenant. Par conséquent, dans un mélange de gaz, la pression totale dans le contenant est la somme des pressions partielles des gaz composants, en supposant un comportement de gaz idéal et aucune réaction chimique entre les composants. Cette loi est connue sous le nom de loi des pressions partielles de Dalton. La théorie a été établie par le scientifique anglais John Dalton (1766-1844). La loi de Dalton est cohérente avec le fait que les pressions s'additionnent, conformément au principe de Pascal. Dans un mélange de gaz idéaux en équilibre thermique, le nombre de molécules de chaque gaz est proportionnel à sa pression partielle.

Une autre application importante de la pression partielle est la pression de vapeur, qui est la pression partielle d'une vapeur à laquelle elle est en équilibre avec la phase liquide de la même substance. À n'importe quelle température, la pression partielle de l'eau dans l'air ne peut pas dépasser la pression de vapeur de l'eau à cette température, car chaque fois que la pression partielle atteint la pression de vapeur, l'eau se condense hors de l'air. La rosée est un exemple de cette condensation. La température à laquelle la condensation se produit pour un échantillon d'air est appelée le point de rosée. Il est facilement mesuré en refroidissant lentement une boule de métal ; le point de rosée est la température à laquelle la condensation apparaît pour la première fois sur la boule.

La loi des pressions partielles de Dalton

La pression partielle d'un gaz est une mesure de l'activité thermodynamique des molécules du gaz. La pression qu’un gaz créerait s’il occupait ...

Education

Enseignement

JoVE Core

Physics

Physique

Unit 1

Unité 1

The Kinetic Theory of Gases

La théorie cinétique des gaz

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

gas mixtures and their partial pressures

Gas mixtures have a total pressure that comes from the partial pressures of each gas. A partial pressure is the pressure one gas would make if it filled the whole container by itself. This idea helps explain how gases behave when they are mixed together.

When two or more gases share a container, their molecules move randomly and collide with one another. If the gases are at the same temperature, they reach thermal equilibrium. Their molecules then have the same average kinetic energy. In that case, each gas follows the ideal gas law separately and pushes on the walls of the container on its own.

The total pressure in the container is the sum of the partial pressures of the component gases. This result is called Dalton's law of partial pressures. It applies when the gases behave like ideal gases and do not react chemically with one another. The law was developed by the English scientist John Dalton, who lived from 1766 to 1844. It also agrees with Pascal's principle, which says that pressures add up.

Partial pressure also helps describe vapor pressure. Vapor pressure is the partial pressure of a vapor when it is in equilibrium with the liquid form of the same substance. In air, the partial pressure of water cannot rise above the vapor pressure of water at that temperature. If it reaches that value, water condenses out of the air. Dew is one common example of this process.

The temperature where condensation begins in a sample of air is called the dew point. One simple way to measure it is to cool a metal ball slowly. The dew point is the temperature at which condensation first appears on the ball.

Gas Mixtures and Their Partial Pressures

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Gas mixtures have a total pressure that comes from the partial pressures of each gas. A partial pressure is the pressure one gas would make if it filled the whole container by itself. This idea helps explain how gases behave when they are mixed together. When two or more gases share a container, their molecules move randomly and collide with one another. If the gases are at the same temperature, they reach thermal equilibrium. Their molecules then have the same average kinetic energy. In that...

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key terms and concepts

Learn how gas mixtures share pressure through partial pressures, how Dalton's law works, and how vapor pressure and dew point explain condensation in air.

Gas Mixtures and Their Partial Pressures | JoVE K12

physics

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Gas Mixtures and Their Partial Pressures

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