Gas mixtures and partial pressures | AP Chemistry | Khan Academy

TL;DR

The total pressure in a container with multiple gases is equal to the sum of the partial pressures contributed by each gas.

Transcript

• [Instructor] In this video, we're going to introduce ourselves to the idea of partial pressure due to ideal gases. And the way to think about it is imagine some type of a container, and you don't just have one type of gas in that container. You have more than one type of gas. So let's say you have gas one that is in this white color. And obviousl... Read More

Key Insights

• 🫢 The total pressure in a container with multiple gases can be calculated by summing up the partial pressures from each gas.
• 🫢 The ideal gas law relates pressure, volume, number of moles, gas constant, and temperature.
• #️⃣ The mole fraction is the ratio of the number of moles of a specific gas to the total number of moles and can be used to determine partial pressures.

Questions & Answers

Q: How is the total pressure in a container with multiple gases calculated?

The total pressure is calculated by summing up the partial pressures contributed by each gas in the container. This is based on the observation that the total pressure is equal to the pressure each gas would exert on its own.

Q: How does the ideal gas law relate to partial pressures?

The ideal gas law, which states that pressure times volume is equal to the number of moles times the ideal gas constant times temperature, can be rearranged to show that the total pressure is equal to the total number of moles times the gas constant times temperature divided by volume.

Q: What is a mole fraction?

A mole fraction is the ratio of the number of moles of a specific gas to the total number of moles in a mixture. It can be used to determine the partial pressure of a gas, as the partial pressure is equal to the mole fraction multiplied by the total pressure.

Q: How can information about the total pressure, total number of moles, and number of moles of a specific gas be used to find the partial pressure?

By using the equation for the mole fraction, which is the number of moles of a specific gas divided by the total number of moles, and knowing that the partial pressure over the total pressure is equal to the mole fraction, the partial pressure of the gas can be calculated.

Summary & Key Takeaways

• The total pressure exerted on the inside of a container is equal to the sum of partial pressures from each gas present.

• The ideal gas law can be used to mathematically express the relationship between pressure, volume, number of moles, gas constant, and temperature.

• The mole fraction, which represents the ratio of the number of moles of a specific gas to the total number of moles, can be used to determine the partial pressure of that gas.