Question 1

Which of the following correctly expresses the Ideal Gas Law, and what are the standard units for each variable?

Accepted Answer

$$PV = nRT$$; $$P in $$atm, $$V in L$$, $$n in $$mol, $$T in K$$

Question 2

At standard temperature and pressure (STP), what is the molar volume of an ideal gas?

Accepted Answer

$$22.4\ L$$

Question 3

A sample of helium gas has a mass of $$4.00\ g$$ and occupies $$22.4\ L at $$STP. What is its density?

Accepted Answer

$$0.179\ g/L$$

Question 4

Which of the following statements about gas density is correct?

Accepted Answer

The density of a gas is directly proportional to its molar mass.

Question 5

A $$3.45\ g$$ sample of an unknown gas occupies $$0.597\ L at$$ $$75.00^\circ C$$ and $$1.5\ atm. $$What is the molar mass of the gas? (Use $$R = 0.08206\ L\cdot atm/(mol\cdot K))$$

Accepted Answer

$$110\ g/mol$$

Question 6

Which equation would you use to calculate the number of moles of a gas given its pressure, volume, and temperature?

Accepted Answer

$$n = \frac{PV}{RT}$$

Question 7

A mixture of gases contains $$2.0\ mol of$$ $$N_2$$, $$1.0\ mol of$$ $$O_2$$, and $$1.0\ mol of$$ $$CO_2 in a$$ $$10.0\ L$$ container at $$300\ K. $$What is the total pressure of the mixture? ($$R = 0.08206\ L\cdot atm/(mol\cdot K))$$

Accepted Answer

$$9.84\ atm$$

Question 8

Dalton’s Law of Partial Pressures states that:

Accepted Answer

The total pressure of a mixture of gases is equal to the sum of the partial pressures of each individual gas.

Question 9

If the mole fraction of $$N_2 in $$air is $$0.78$$ and the atmospheric pressure is $$1.00\ atm$$, what is the partial pressure of $$N_2$$?

Accepted Answer

$$0.78\ atm$$

Question 10

A reaction vessel contains $$N_2(g$$)$$ and 3H_2(g$$)$$ at constant volume and temperature. If the reaction N_2$(g) + 3H_2(g) \rightarrow 2NH_3(g)$$ goes to completion, what happens to the total pressure?

Accepted Answer

The total pressure decreases because the total number of gas molecules decreases.

Question 11

Methanol ($$CH_3OH) $$can be synthesized by the reaction: $$CO(g) + 2H_2(g) \rightarrow CH_3OH(g). $$What volume of $$H_2$$ gas at $$355\ K$$ and $$738\ mmHg is $$needed to synthesize $$35.7\ g of $$methanol? ($$R = 0.08206\ L\cdot atm/(mol\cdot K)$$, $$1\ atm = 760\ mmHg$$, $$M_{CH_3OH} = 32.04\ g/mol)$$

Accepted Answer

$$66.9\ L$$

Question 12

Which of the following best describes the relationship between the partial pressure of a gas and its mole fraction in a mixture?

Accepted Answer

$$P_a = X_a P_{total}$$

Question 13

A $$5.00\ g$$ sample of an unknown gas occupies $$2.00\ L at$$ $$1.00\ atm$$ and $$273.15\ K. $$What is the molar mass of the gas?

Accepted Answer

$$56.0\ g/mol$$

Question 14

Which of the following is NOT an assumption of the ideal gas law?

Accepted Answer

Gas particles have significant volume compared to the container.

Question 15

If you double the temperature (in Kelvin) of an ideal gas while keeping pressure constant, what happens to the volume?

Accepted Answer

The volume doubles.

Question 16

A $$10.0\ L$$ container holds a mixture of $$2.0\ mol$$ $$N_2$$ and $$3.0\ mol$$ $$O_2 at$$ $$300\ K. $$What is the mole fraction of $$O_2$$?

Accepted Answer

$$0.60$$

Question 17

Which of the following real-world scenarios best illustrates Dalton’s Law of Partial Pressures?

Accepted Answer

The total pressure inside a scuba tank is the sum of the pressures from oxygen and nitrogen gases.

Question 18

If the pressure of a gas is measured as $$738\ mmHg$$, what is this pressure in atmospheres?

Accepted Answer

$$0.971\ atm$$

Question 19

Which of the following would increase the density of a gas, assuming all other variables are held constant?

Accepted Answer

Increasing the molar mass of the gas.

6.5-6.7 : Gases – Ideal Gas Law, Molar Volume, Density, and Partial Pressure

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