Gases

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AP Chemistry › Gases

Questions 1 - 10
1

Under which conditions would you expect Ar to deviate the most from ideal behavior?

200 K and 1 atm

200 K and 10 atm

300K and 5 atm

300K and 10 atm

Ar always behaves ideally

Explanation

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At 200K (lowest temperature in the list, and the highest pressure). This gives Ar the most time to interact due to molecular speeds and the high pressure implies the molecular size is not insignificant relative to the container.

2

Would you expect a polar or non polar gas to deviate most from ideal gas behavior?

Non polar gases, because of high dispersion interactions

Polar gases, because of high dipole-dipole interactions

Non polar gases because of reduced overall intermolecular forces

Polar gases because of hydrogen bonding

Both polar and non polar gases behave ideally

Explanation

Polar gases would have increased interactions due to their dipoles that would lead to deviations from ideal gas behavior.

3

When does a gas behave most like an ideal gas?

At low temperatures, low volume, low intermolecular interactions

At high temperatures, high volume, low intermolecular interactions

At low volumes, high temperatures, and high intermolecular interactions

At high temperature, high volumes, and high intermolecular interactions

At low temperatures, high volume, and low intermolecular interactions

Explanation

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At high temperatures the gas molecules are moving fast enough to shorten the time scale for any interactions. At high volumes, the molecular size becomes small relative to the size of the container, and the low interactions mean the molecules act more independently.

4

When does a gas behave most like an ideal gas?

At low temperatures, low volume, low intermolecular interactions

At high temperatures, high volume, low intermolecular interactions

At low volumes, high temperatures, and high intermolecular interactions

At high temperature, high volumes, and high intermolecular interactions

At low temperatures, high volume, and low intermolecular interactions

Explanation

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At high temperatures the gas molecules are moving fast enough to shorten the time scale for any interactions. At high volumes, the molecular size becomes small relative to the size of the container, and the low interactions mean the molecules act more independently.

5

Under which conditions would you expect Ar to deviate the most from ideal behavior?

200 K and 1 atm

200 K and 10 atm

300K and 5 atm

300K and 10 atm

Ar always behaves ideally

Explanation

The ideal gas law assumes the gas particles are non-interacting and small relative to the size of their container. At 200K (lowest temperature in the list, and the highest pressure). This gives Ar the most time to interact due to molecular speeds and the high pressure implies the molecular size is not insignificant relative to the container.

6

Would you expect a polar or non polar gas to deviate most from ideal gas behavior?

Non polar gases, because of high dispersion interactions

Polar gases, because of high dipole-dipole interactions

Non polar gases because of reduced overall intermolecular forces

Polar gases because of hydrogen bonding

Both polar and non polar gases behave ideally

Explanation

Polar gases would have increased interactions due to their dipoles that would lead to deviations from ideal gas behavior.

7

Which of the following gases will have the highest rate of effusion?

Helium

Oxygen

Nitrogen

Carbon dioxide

Sulfur dioxide

Explanation

The rate of effusion for a gas is inversely proportional to the square-root of its molecular mass (Graham's Law).

The gas with the lowest molecular weight will effuse the fastest.

Oxygen:

Nitrogen:

Carbon dioxide:

Sulfur dioxide:

Helium:

The lightest, and therefore fastest, gas is helium.

8

Which of the following gases will have the highest rate of effusion?

Helium

Oxygen

Nitrogen

Carbon dioxide

Sulfur dioxide

Explanation

The rate of effusion for a gas is inversely proportional to the square-root of its molecular mass (Graham's Law).

The gas with the lowest molecular weight will effuse the fastest.

Oxygen:

Nitrogen:

Carbon dioxide:

Sulfur dioxide:

Helium:

The lightest, and therefore fastest, gas is helium.

9

If the pressure of a sample of one mole of an ideal gas is increased from 2atm to 3atm at a constant volume, and the initial temperature was 20˚C, what is the final temperature of the sample?

439.5K

30K

195.3K

303K

Explanation

Because the mass and volume of the sample of the ideal gas are kept constant, a change in pressure causes only a direct change in the temperature. This can be derived from the following ideal gas equation:.

10

If the pressure of a sample of one mole of an ideal gas is increased from 2atm to 3atm at a constant volume, and the initial temperature was 20˚C, what is the final temperature of the sample?

439.5K

30K

195.3K

303K

Explanation

Because the mass and volume of the sample of the ideal gas are kept constant, a change in pressure causes only a direct change in the temperature. This can be derived from the following ideal gas equation:.

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