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

Considera un gas all'interno di un contenitore. La pressione esercitata dal gas è la somma delle forze esercitate a causa delle collisioni molecolari tra le sue molecole e la superficie circostante.
Un gas con molte molecole esercita una pressione maggiore rispetto a un gas con un numero inferiore di molecole nello stesso contenitore. Quindi, la pressione del singolo componente è chiamata pressione parziale.
Si consideri una miscela di gas ideali in un contenitore all'equilibrio termico. La pressione totale all'interno del contenitore è uguale alla somma delle pressioni parziali dei suoi componenti. Questa osservazione è nota come legge di Dalton delle pressioni parziali.
Richiamando l'equazione del gas ideale e sostituendo le pressioni parziali dei singoli gas, è possibile determinare la pressione totale.
La pressione parziale di un vapore che è in equilibrio con la fase liquida della stessa sostanza è chiamata tensione di vapore.
Il rapporto tra la pressione parziale del vapore acqueo e la pressione del vapore dell'acqua a una temperatura è noto come umidità relativa.

<ol>
	<li>OpenStax. (2019). Fisica universitaria Vol. 2. [Versione web], pag 37 - 38. Estratto da <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>

legge delle pressioni parziali di dalton

Dalton's Law of Partial Pressure

La pressione parziale di un gas è una misura dell'attività termodinamica delle molecole del gas. La pressione che un gas creerebbe se occupasse il volume totale disponibile è chiamata pressione parziale del gas. Se due o più gas sono miscelati insieme in un contenitore, le molecole si muovono casualmente e collidono tra loro, causando il raggiungimento dell'equilibrio termico. Quando i gas hanno la stessa temperatura, le loro molecole hanno la stessa energia cinetica media. Pertanto, ciascun gas obbedisce alla legge dei gas ideali separatamente ed esercita la stessa pressione sulle pareti del contenitore individualmente. Di conseguenza, in una miscela di gas, la pressione totale nel contenitore è la somma delle pressioni parziali dei gas componenti, assumendo un comportamento di gas ideale e nessuna reazione chimica tra i componenti. Questa legge è conosciuta come legge delle pressioni parziali di Dalton. La teoria è stata stabilita dallo scienziato inglese John Dalton (1766-1844). La legge di Dalton è coerente con il fatto che le pressioni si sommano, secondo il principio di Pascal. In una miscela di gas ideali in equilibrio termico, il numero di molecole di ciascun gas è proporzionale alla sua pressione parziale.

Un'altra importante applicazione della pressione parziale è la pressione di vapore, che è la pressione parziale di un vapore alla quale è in equilibrio con la fase liquida della stessa sostanza. Ad ogni temperatura, la pressione parziale dell'acqua nell'aria non può superare la pressione di vapore dell'acqua a quella temperatura, poiché ogni volta che la pressione parziale raggiunge la pressione di vapore, l'acqua si condensa dall'aria. La rugiada è un esempio di questa condensazione. La temperatura alla quale si verifica la condensazione per un campione di aria è chiamata punto di rugiada. È facilmente misurabile raffreddando lentamente una sfera di metallo; il punto di rugiada è la temperatura alla quale la condensazione appare per la prima volta sulla sfera.

Legge delle pressioni parziali di Dalton

La pressione parziale di un gas è una misura dell'attività termodinamica delle molecole del gas. La pressione che un gas creerebbe se occupasse ...

Education

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JoVE Core

Physics

Fisica

Unit 1

Unità 1

The Kinetic Theory of Gases

La teoria cinetica dei gas

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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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

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Gas Mixtures and Their Partial Pressures

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