Question Video: Identifying the Correct Definition of the Standard Molar Gas Volume | Nagwa Question Video: Identifying the Correct Definition of the Standard Molar Gas Volume | Nagwa

Question Video: Identifying the Correct Definition of the Standard Molar Gas Volume Chemistry • First Year of Secondary School

Join Nagwa Classes

Attend live Chemistry sessions on Nagwa Classes to learn more about this topic from an expert teacher!

Which of the following is the correct definition of the standard molar gas volume? [A] It is the volume occupied by one mole of any gas divided by temperature and pressure. [B] It is the volume occupied by one mole of any gas at a given temperature and pressure. [C] It is the volume occupied by one gram of any gas divided by temperature and pressure. [D] It is the volume occupied by one gram of any gas at a given temperature and pressure.

04:57

Video Transcript

Which of the following is the correct definition of the standard molar gas volume? (A) It is the volume occupied by one mole of any gas divided by temperature and pressure. (B) It is the volume occupied by one mole of any gas at a given temperature and pressure. (C) It is the volume occupied by one gram of any gas divided by temperature and pressure. (D) It is the volume occupied by one gram of any gas at a given temperature and pressure.

In chemistry, there are many laws and rules that help us understand the complex chemical relationships that are used every day in the field. One of these laws, known as Avogadro’s law, is used in chemistry to help us understand the relationship between the volume of a gas and the number of moles of the same gas.

Avogadro’s law states that at a constant temperature and pressure, both the volume and number of moles of a gas are directly proportional. We can express Avogadro’s law by using the following proportionality statement: 𝑉 is proportional to 𝑛. 𝑉 is the volume of the gas, and 𝑛 is the number of moles of the gas. We can also express Avogadro’s law as an equation when we want to perform calculations using the law shown as 𝑉 equals 𝑛 multiplied by 𝑉 𝑚, where 𝑛 is the number of moles and 𝑉 𝑚 is a proportionality constant that represents molar volume. Molar volume is defined as the volume occupied by one mole of gas at a specific temperature and pressure and is typically expressed as liters per mole.

Since we cannot see gas, the concept of Avogadro’s law and molar volume may be difficult to grasp initially. So let’s look at an example using a chemical equation that describes the formation of water vapor from hydrogen and oxygen gas.

As we can see in the equation, two moles of hydrogen gas react with one mole of oxygen gas to form two moles of water vapor. And as we know from Avogadro’s law, since the number of moles of gas is proportional to the volume of gas, we can also say that the equation indicates the volumes that react as well. For example, using this equation, we can say that two volumes of hydrogen gas react with one volume of oxygen gas to produce two volumes of water vapor. We can further express this as a ratio of two to one to two, hydrogen to oxygen to water vapor, with the understanding that this ratio will remain constant regardless of whether it is expressed in moles or units of volume. This is the case as long as the given temperature and pressure also remain constant.

Now that we have some background information, we can focus on our question. Our question asks what the best definition of standard molar gas volume is given a variety of choices.

If we go through our list, we can immediately eliminate answer choices (C) and (D) as they mention the volume of one gram of gas. As molar volume deals only with the volume of moles and not mass, we can easily see that these choices cannot be correct. Answer choice (A) correctly mentions the volume of one mole of gas. However, it mentions that this value is divided by temperature and pressure. This is incorrect because Avogadro’s law states that temperature and pressure must only be constant, not manipulated as variables in the equation.

Therefore, only answer choice (B), it is the volume occupied by one mole of any gas at a given temperature and pressure, matches with the definition of standard molar gas volume. “It is the volume occupied by one mole of any gas at a given temperature and pressure” is the correct answer.

Join Nagwa Classes

Attend live sessions on Nagwa Classes to boost your learning with guidance and advice from an expert teacher!

• Interactive Sessions
• Chat & Messaging
• Realistic Exam Questions

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy