Name: gas pressure in mixtures: partial pressures
Uploaded: 2020-09-03T13:38:26.000Z
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PS.Chm.7.3

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

Давление чистого газа это сумма столкновений молекул между его частицами и окружающими поверхностями. Образец газа с меньшим количеством частиц в данном объеме оказывает более низкое давление, чем образец с большим количеством частиц в том же объеме. Но сколько составляет давление смеси разных газов?Для многокомпонентной газовой смеси давление представляет собой сумму столкновений всех молекул газа. Предполагается, что каждый компонент в смеси оказывает собственное давление, которое не зависит от других присутствующих газов. Давление любого отдельного компонента называется его парциальным давлением.Полное давление идеальной газовой смеси равно сумме парциального давления ее компонентов. Это наблюдение является законом парциальных давлений Дальтона. Применяя закон идеального газа, парциальные давления отдельных компонентов газа заменяются измеряемыми величинами.Поскольку газы в смеси занимают один и тот же объем и имеют одинаковую температуру, уравнение можно упростить. Сумма молей отдельных компонентов равна общему количеству молей всех компонентов газа, n-общее. Следовательно, полное давление газовой смеси равно n-общему, умноженному на постоянную R-T, деленную на V.Число молей компонента, деленное на общее количество молей в смеси, является мольной долей.Преобразование мольной доли для общего количества молей и замена n-общего в законе парциальных давлений Дальтона дает выражения для общего давления. Следующая перегруппировка показывает, что парциальное давление газа в смеси является произведением его мольной доли и общего давления смеси. Таким образом, в газовой смеси парциальное давление любого компонента i равно мольной доле i, умноженной на общее давление.В качестве примера расчета предположим, что емкость, заполненная двумя газами гелием и аргоном содержит 40%по объему аргона. Это означает, что мольная доля аргона составляет 0, 4. Если полное давление составляет 4 атмосфер, сколько составляет парциальное давление гелия?Используя уравнение для парциального давления газа, парциальное давление аргона равно его мольной доле, умноженной на общее давление. Таким образом, 0, 4 умноженное на 4 атмосферы дает парциальное давление аргона 1, 6 атмосфер. Поскольку сумма парциальных давлений равна общему давлению, уравнение можно изменить так, чтобы парциальное давление аргона можно было вычесть из общего давления.Таким образом, парциальное давление гелия составляет 2.4 атмосфер.

Смесь газов - закон парциальных давлений Дальтона

Если отдельные газы не вступают в химическую реакцию друг с другом, отдельные газы в смеси газов не влияют на давление друг друга. Каждый газ в смеси оказывает такое же давление, какое он оказывал бы, если бы он находился в контейнере отдельно. Давление, оказываемое каждым отдельным газом в смеси, называется его парциальным давлением. 
 
 Это означает, что в смеси, содержащей три разных газа A, B и C, если P A - парциальное давление газа A; P B - парциальное давление газа B; P C - парциальное давление газа C; тогда полное давление определяется уравнением 1: & nbsp; 
 
 <img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-01.png" style="height: 40px;" />
 
 Это закон парциальных давлений Дальтона: полное давление смеси идеальных газов равно сумме парциальных давлений составляющих газов. 
 
 Пусть n A , n B и n C - количество молей каждого из газов в смеси. Если каждый газ подчиняется уравнению идеального газа, парциальное давление можно записать как: 
 
 <img alt = "Eq2" src = "https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-02.png" style = "height: 40px ; " /> 
 
 Поскольку все газы имеют одинаковую температуру и занимают одинаковый объем, подстановка в уравнение 1 дает: 
 
 <img alt = "Eq3" src = "https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-03.png" style = "height: 40px ; " /> 
 
 Уравнение показывает, что при постоянной температуре и постоянном объеме полное давление пробы газа определяется общим количеством присутствующих молей газа. 
 
 Для смесей газов удобно вводить величину, называемую мольной долей, & chi ;, которая определяется как количество молей определенного вещества в смеси, деленное на общее количество молей всех присутствующих веществ. Математически мольная доля вещества A в смеси с B и C выражается как 
 
 <img alt="Eq4" src="https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-04.png" style="height: 40px;" />
 
 Точно так же мольные доли B и C: 
 
 <img alt="Eq5" src="https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-05.png" style="height: 40px;" />
 
 <img alt="Eq6" src="https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-06.png" style="height: 40px;" />
 
 Объединение уравнения для мольной доли A и уравнения для парциального давления дает: 
 
 <img alt = "Eq7" src = "https://www.jove.com/files/core/CDNSource/lessons/1038/1038_Equations-07.png" style = "height: 40px ; " /> 
 
 Парциальное давление газа A связано с общим давлением газовой смеси через его мольную долю. 
 
 Другими словами, давление газа в смеси газов является произведением его мольной доли и общего давления смеси. 
 
 Этот текст адаптирован из <a href = "https://openstax.org/books/chemistry-2e/pages/9-3-stoichiometry-of-gaseous-substances-mixtures-and-reactions" > Openstax, Химия 2е изд., Раздел 9.3: Стехиометрия газообразных веществ, смесей и реакций. </a>

Если отдельные газы не вступают в химическую реакцию друг с другом, то отдельные газы в смеси газов не влияют на давление друг друга. Каждый газ...

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KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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

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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...

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Stoichiometry of Gases with the Ideal Gas Law

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Gas Pressure in Mixtures: Partial Pressures

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