Name: gas pressure in mixtures: partial pressures
Uploaded: 2020-09-03T13:38:26.000Z
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K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.3

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Mixtures of Gases: Dalton's Law of Partial Pressures and Mole Fractions

La presión de un gas puro es la suma de las colisiones moleculares entre sus partículas y contra las superficies que lo rodean. Una muestra de gas con menos partículas en un volumen dado ejerce menos presión que una muestra con más partículas en el mismo volumen. Pero cuál es la presión de una mezcla de distintos gases?En una mezcla gaseosa con multiples componentes, la presión es la suma de las colisiones de todas las moléculas gaseosas. Se asume que cada componente que constituye la mezcla ejerce su propia presión, la cual es independiente de los otros gases que están presentes. La presión de cualquier componente individual se llama presión parcial.La presión total de la mezcla de un gas ideal es igual a la suma de las presiones parciales de sus componentes. Esta observación se conoce como la ley de presiones parciales de Dalton. Si se aplica la ley de los gases ideales, las presiones parciales de los componentes gaseosos individuales se sustituyen por variables medibles.Como los gases de la mezcla ocupan el mismo volumen y están a la misma temperatura, la ecuación se puede simplificar. La suma de los moles de los componentes individuales es igual al número total de moles de todos los componentes gaseosos, n total. Por lo tanto, la presión total de una mezcla gaseosa es igual a la n total multiplicada por la constante R-T sobre V.El número de moles de un componente dividido entre los moles totales de la mezcla se llama fracción molar.Si se reorganiza la fracción molar para los moles totales y se sustituye la n total en la ley de Dalton de presiones parciales, da como resultado expresiones para calcular la presión total. Si se vuelve a reorganizar, la presión parcial de un gas en una mezcla es el producto de su fracción molar y la presión total de la mezcla. Entonces, en una mezcla gaseosa, la presión parcial de cualquier componente, i, es igual a la fracción molar de i multiplicado por la presión total.Un ejemplo de un cálculo sería el siguiente:supongamos que un contenedor está lleno de dos gases, helio y argón, y 40%de su volumen es argón. Esto implica que la fracción molar del argón es de 0, 4. Si la presión total es de 4 atmósferas, cuál es la presión parcial del helio?Si usamos la ecuación de las presiones parciales de un gas, la presión parcial del argón es igual a su fracción molar multiplicada por la presión total. Por consiguiente, 0, 4 por 4 atmósferas da como resultado que la presión parcial del argón es de 1, 6 atmósferas. Como la suma de las presiones parciales es igual a la presión total, la ecuación se puede reorganizar de modo que la presión parcial del argón se pueda restar de la presión total.Así, la presión parcial del helio es de 2, 4 atmósferas.

mezcla de gases - ley de las presiones parciales de dalton

A menos que los gases individuales reaccionen químicamente entre sí, los gases individuales de una mezcla de gases no afectan la presión de los demás. Cada gas en una mezcla ejerce la misma presión que ejercería si estuviera presente solo en el recipiente. La presión ejercida por cada gas individual en una mezcla se denomina presión parcial.
 
 Esto significa que en una mezcla que contiene tres gases diferentes A, B y C, si PA es la presión parcial del gas A; PB es la presión parcial del gas B; PC es la presión parcial del gas C; entonces, la presión total viene dada por la ecuación 1: 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-01.png" style="height: 40px;" />
 
 Esta es la ley de las presiones parciales de Dalton: La presión total de una mezcla de gases ideales es igual a la suma de las presiones parciales de los gases componentes.
 
 Siendo nA, nB y nC el número de moles de cada uno de los gases en la mezcla. Si cada gas obedece la ecuación de los gases ideales, la presión parcial se puede escribir como:
 
 <img alt="Eq2" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-02.png" style="height: 40px;" />
 
 Puesto que todos los gases están a la misma temperatura y ocupan el mismo volumen, al sustituir la ecuación 1 se obtiene:
 
 <img alt="Eq3" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-03.png" style="height: 40px;" />
 
 La ecuación indica que a temperatura constante y volumen constante, la presión total de una muestra de gas está determinada por el número total de moles de gas presente.
 
 Para las mezclas de gases, conviene introducir una cantidad denominada fracción molar, χ, que se define como el número de moles de una sustancia determinada en una mezcla dividida por el número total de moles de todas las sustancias presentes. Matemáticamente, la fracción molar de una sustancia A en una mezcla con B y C se expresa como
 
 <img alt="Eq4" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-04.png" style="height: 40px;" />
 
 De forma similar, la fracción molar de B y C son:
 
 <img alt="Eq5" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-05.png" style="height: 40px;" />
 
 <img alt="Eq6" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-06.png" style="height: 40px;" />
 
 Al combinar la ecuación para la fracción molar de A y la ecuación para la presión parcial se obtiene:
 
 <img alt="Eq7" src="https://www.jovecore.com/CDNSource/lessons/1038/1038_Equations-07.png" style="height: 40px;" />
 
 La presión parcial del gas A está relacionada con la presión total de la mezcla de gases a través de su fracción molar.
 
 En otras palabras, la presión de un gas en una mezcla de gases es el producto de su fracción molar y la presión total de la mezcla.
 
 Este texto ha sido adaptado de <a href="https://openstax.org/books/chemistry-2e/pages/9-3-stoichiometry-of-gaseous-substances-mixtures-and-reactions">Openstax, Química 2e, Sección 9.3: Estequiometría de las Sustancias gaseosas, Mezclas y Reacciones.</a>

Mezcla de Gases - Ley de las Presiones Parciales de Dalton

A menos que los gases individuales reaccionen químicamente entre sí, los gases individuales en una mezcla de gases no afectan la presión de los demás. Cada gas ...

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KEY TERMS AND CONCEPTS

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gas pressure in mixtures: partial pressures

Gas pressure in mixtures is described by partial pressure and mole fraction. When gases do not chemically react, each gas in the mixture acts as if it were alone in the container. The pressure from one gas is called its partial pressure.

For a mixture of three gases, A, B, and C, the total pressure equals the sum of their partial pressures: PA, PB, and PC. This is Dalton's law of partial pressures. It states that the total pressure of a mixture of ideal gases is the sum of the pressures from each gas.

If each gas follows the ideal-gas equation, its partial pressure can be written in terms of moles, temperature, and volume. Because every gas in the mixture has the same temperature and takes up the same volume, these terms can be combined. At constant temperature and constant volume, the total pressure depends on the total number of moles of gas present.

For gas mixtures, chemists also use mole fraction, x. Mole fraction is the number of moles of one substance divided by the total number of moles in the mixture. For gas A in a mixture with B and C, the mole fractions of A, B, and C are found in this way.

Mole fraction also links directly to partial pressure. The partial pressure of gas A equals its mole fraction times the total pressure of the mixture. In other words, a gas's pressure in a mixture is its share of the total pressure.

Gas Pressure in Mixtures: Partial Pressures

gas-pressure-in-mixtures-partial-pressures

definition and measurement of pressure: atmospheric pressure, barometer, and manometer

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Pressure Units and Tools for Gas Measurement

Pressure is the force applied to a given area, and gas pressure comes from gas molecules colliding with surfaces. Each collision is tiny, but many collisions over a small area can create high pressure. Pressure increases when force increases or when the area gets smaller. It decreases when force drops or when the area gets larger. Pressure is measured in pascals, or Pa, in the SI system. One pascal equals 1 newton per square meter, and a newton is a unit of force equal to 1 kg·m/s2. A pascal...

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How Gas Pressure, Volume, and Temperature Change

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applications of the ideal gas law: molar mass, density, and volume

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Ideal Gas Law at STP and Gas Density

The ideal gas law links pressure, volume, number of moles, and temperature. It helps explain how gas volume changes when pressure or temperature changes. At standard temperature and pressure, or STP, the values are 273.15 K and 1 atm. At STP, one mole of an ideal gas occupies about 22.4 L. This is called the standard molar volume. The gas can be hydrogen, oxygen, argon, or carbon dioxide, and the volume is still about 22.4 liters. Half a mole occupies 11.2 L, and 2 moles occupy 44.8 L. The...

mixtures of gases: dalton's law of partial pressures and mole fractions

Gas pressure in mixtures is described by partial pressure and mole fraction. When gases do not chemically react, each gas in the mixture acts as if it were alone in the container. The pressure from one gas is called its partial pressure. For a mixture of three gases, A, B, and C, the total pressure equals the sum of their partial pressures: PA, PB, and PC. This is Dalton's law of partial pressures. It states that the total pressure of a mixture of ideal gases is the sum of the pressures from...

chemical stoichiometry and gases: using ideal gas law to determine moles

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Stoichiometry of Gases with the Ideal Gas Law

Chemical stoichiometry links the amounts of reactants and products in a chemical reaction. For gases, those amounts can also be measured by volume. If a gas’s volume, pressure, and temperature are known, the ideal gas equation can be used to find the number of moles present. The same idea works in reverse. If the moles of a gas are known, its volume can be found at any temperature and pressure. The transcript gives an example using 8.88 g of gallium reacting with excess hydrochloric acid.

basic postulates of kinetic molecular theory: particle size, energy, and collision

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Kinetic Molecular Theory and Gas Behavior

Kinetic molecular theory explains gas behavior at the particle level. It gives a microscopic model for what happens when pressure or temperature changes. Gas laws describe how macroscopic properties change, but they do not explain why those changes happen. The theory was put into a complete form by Rudolf Clausius in 1857. It was built from hundreds of experimental observations about gases. Those observations helped explain the different gas laws through a few basic postulates. One key idea...

kinetic molecular theory and gas laws explain properties of gas molecules

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kinetic molecular theory: molecular velocities, temperature, and kinetic energy

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key terms and concepts

Learn how partial pressure and mole fraction describe gas mixtures, and how Dalton's law connects each gas to the total pressure.

Gas Pressure in Mixtures: Partial Pressures | JoVE K12

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CHEM.10

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New York State Science Learning Standards

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Physical Properties of Matter

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Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

First Law of Thermodynamics

Energy Conservation

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Internal Energy

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Quantifying Heat

Thermal Energy&#160;

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Enthalpy

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Thermochemical Equations

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Constant Pressure Calorimetry

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PS.Chm.7.2

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Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion

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Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

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Ideal Gas Law

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
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Understand the relationship among pressure, temperature, volume, and phase.

Gas Pressure in Mixtures: Partial Pressures

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