Question 1

A sample of nitrogen gas occupies 2.50 L at 1.00 atm and 300 K. If the pressure is increased to 2.00 atm and the temperature is raised to 400 K, what will be the new volume of the gas? (Assume the amount of gas remains constant.)

Use the Combined Gas Law: $$\frac{P_1$ V_1$}{T_1$} = \frac{P_2$ V_2$}{T_2$}$$

Accepted Answer

1.25 L

Question 2

A weather balloon contains 60.0 L of helium at 1.00 atm and 273 K. If the temperature increases to 546 K and the pressure remains constant, what will be the new volume of the balloon?

Use: $$\frac{V_1$}{T_1$} = \frac{V_2$}{T_2$}$$

Accepted Answer

120.0 L

Question 3

A 0.250 mol sample of oxygen gas occupies 5.60 L at STP. What is the molar volume of a gas at STP?

Recall: 1 mole of gas at STP occupies $$22.4 L.$$

Accepted Answer

22.4 L

Question 4

Calculate the molar mass of C2H6O (ethanol).

Use: $$	ext{Molar mass} = 2 	imes 12.01 + 6 	imes 1.01 + 1 	imes 16.00$$

Accepted Answer

46.08 g/mol

Question 5

What is the volume at STP of 4.00 g of CH4 (molar mass = 16.04 g/mol)?

Use: $$	ext{Volume at STP} = \frac{	ext{moles}}{1} 	imes 22.4 L$$

Accepted Answer

5.60 L

Question 6

A scuba tank contains a mixture of helium and oxygen at a total pressure of 8.00 atm. If the partial pressure of oxygen is 1280 mmHg, what is the partial pressure of helium? (1 atm = 760 mmHg)

Use: $$P_{	ext{total}} = P_{	ext{He}} + P$$_{	ext{O}$$_2}$$

Accepted Answer

6.32 atm

Question 7

Which of the following statements best describes Avogadro’s Law?

Accepted Answer

The volume of a gas is directly proportional to the number of moles at constant temperature and pressure.

Question 8

A 2.0 L container holds 0.50 mol of hydrogen gas. If the amount of gas is increased to 1.50 mol at constant temperature and pressure, what is the new volume?

Use: $$\frac{V_1$}{n_1$} = \frac{V_2$}{n_2$}$$

Accepted Answer

6.0 L

Question 9

Which of the following is NOT a correct statement about gases at STP?

Accepted Answer

The pressure at STP is 760 mmHg and 273°C.

Question 10

A mixture of three gases has partial pressures of 2.0 atm, 1.5 atm, and 0.5 atm. What is the total pressure of the mixture?

Use: $$P_{	ext{total}} = P_1$ + P_2$ + P_3$

Accepted Answer

4.0 atm

Question 11

If 3.0 moles of helium are added to a weather balloon already containing 2.0 moles of helium (initial volume 44 L), what is the final volume? (Assume constant T and P)

Use: $$\frac{V_1$}{n_1$} = \frac{V_2$}{n_2$}$$

Accepted Answer

66 L

Question 12

Which of the following best explains why the total pressure of a gas mixture is the sum of the partial pressures of its components?

Accepted Answer

Gas particles in a mixture behave independently and contribute to the total pressure through their own collisions.

Question 13

A 1.00 L sample of gas at 2.00 atm and 300 K is compressed to 0.500 L and heated to 600 K. What is the final pressure?

Use: $$\frac{P_1$ V_1$}{T_1$} = \frac{P_2$ V_2$}{T_2$}$$

Accepted Answer

2.00 atm

Question 14

Which of the following is the correct molar mass for lithium carbonate, Li2CO3?

Use: $$2 	imes 6.94 + 1 	imes 12.01 + 3 	imes 16.00$$

Accepted Answer

73.89 g/mol

Question 15

A gas sample at 1.00 atm and 273 K has a volume of 11.2 L. How many moles of gas are present?

Use: $$	ext{moles} = \frac{	ext{volume}}{22.4}$$

Accepted Answer

0.50 mol

Question 16

A hospital stores oxygen in a 10.0 L tank at 25°C and 5.00 atm. If the gas is used until the pressure drops to 1.00 atm at the same temperature, what volume of oxygen (at 1.00 atm and 25°C) has been used?

Use: $$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Accepted Answer

50.0 L

Gas Laws, Molar Mass, and Dalton’s Law: Study Notes for GOB Chemistry

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