Kinetic Energy of Gases Video Lessons

Concept:

# Problem: Two identical flasks contain O2 and H2 gas, respectively, at the same temperature and pressure. In comparing the two flasks, which of the following is not a true statement.(a) the average kinetic energy of H2 is greater than that of O2(b) the average speed of a H2 molecule is greater than that of an O2(c) the number of impacts/(unit area)/(unit time) are different for the two gases(d) the number of moles is the same(e) total mass of each gas is different

###### FREE Expert Solution

We are asked which of the statements are NOT TRUE given:

Two identical flasks contain O2 and H2 gas, respectively, at the same temperature and pressure.

Analyze each statement:

(a) the average kinetic energy of H2 is greater than that of O2

• The temperature is the same so the average kinetic energy is the same.
• H2 is lighter than O2 so this is FALSE.

(b) the average speed of a H2 molecule is greater than that of an O2

Recall that the molecular speed of a gas is given by:

where R = gas constant, T = temperature, and M = molar mass of the gas.

• We can see that the molar mass is in the denominator.
• This means that the lower the molar mass the faster the molecule is.
• H2 is lighter than O2 so this is TRUE.

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###### Problem Details

Two identical flasks contain O2 and H2 gas, respectively, at the same temperature and pressure. In comparing the two flasks, which of the following is not a true statement.

(a) the average kinetic energy of H2 is greater than that of O2

(b) the average speed of a H2 molecule is greater than that of an O2

(c) the number of impacts/(unit area)/(unit time) are different for the two gases

(d) the number of moles is the same

(e) total mass of each gas is different