Question 1

A sample of neon gas occupies 2.50 L at 1.00 atm and 273 K. If the pressure is increased to 2.00 atm and the temperature is raised to 546 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

2.50 L

Question 2

A weather balloon contains 44.8 L of hydrogen gas at STP. How many moles of hydrogen gas are present?

Recall: At STP, 1 mole of any gas occupies 22.4 L.
$$
	ext{Moles} = \frac{	ext{Volume}}{22.4\,	ext{L}}
$$

Accepted Answer

2.00 moles

Question 3

A 0.500 L sample of gas at 300 K and 1.00 atm is compressed to 0.250 L and heated to 600 K. What is the final pressure?

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

Accepted Answer

2.00 atm

Question 4

A scuba tank contains a mixture of oxygen and nitrogen at a total pressure of 10.0 atm. If the partial pressure of oxygen is 2.0 atm, what is the partial pressure of nitrogen?

Dalton’s Law:
$$
P_{	ext{total}} = P_1$ + P_2$
$$

Accepted Answer

8.0 atm

Question 5

Calculate the molar mass of $$\mathrm{C_2H_6O} ($$ethanol).

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

Accepted Answer

46.08 g/mol

Question 6

What is the volume at STP of 4.00 g of methane ($$\mathrm{CH_4$}$$)?

Molar mass of $$\mathrm{CH_4$} = 16.04 g/$$mol

At STP, 1 mole = 22.4 L.
$$
	ext{Moles} = \frac{4.00}{16.04}
$$
$$
	ext{Volume} = 	ext{moles} 	imes 22.4
$$

Accepted Answer

5.59 L

Question 7

A sample of helium gas has a volume of 0.180 L at 0.800 atm and 29°C. At what temperature (in °C) will the helium have a volume of 90.0 mL and a pressure of 3.20 atm? (n is constant)

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

Accepted Answer

87 K

Question 8

A weather balloon with a volume of 44 L is filled with 2.0 moles of helium. What is the final volume if 3.0 moles of helium are added (total 5.0 moles)?

Avogadro’s Law:
$$
\frac{V_1$}{n_1$} = \frac{V_2$}{n_2$}
$$

Accepted Answer

110 L

Question 9

Which of the following statements about gases at STP is correct?

Accepted Answer

1 mole of any gas occupies 22.4 L at STP.

Question 10

A mixture of gases contains 2.0 atm of nitrogen, 1.0 atm of oxygen, and 0.5 atm of argon. What is the total pressure?

Dalton’s Law:
$$
P_{	ext{total}} = P_1$ + P_2$ + P_3$
$$

Accepted Answer

3.5 atm

Question 11

If 1 mole of helium, 1 mole of oxygen, and 1 mole of nitrogen are each placed in separate balloons at STP, which balloon will have the greatest volume?

Accepted Answer

All will have the same volume.

Question 12

Which of the following best describes Dalton’s Law of Partial Pressures?

Accepted Answer

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

Question 13

A 5.00 L sample of gas at 2.00 atm and 300 K is allowed to expand to 10.0 L at constant temperature. What is the final pressure?

Use Boyle’s Law:
$$
P_1$ V_1$ = P_2$ V_2$
$$

Accepted Answer

1.00 atm

Question 14

Which of the following is NOT a condition of STP?

Accepted Answer

Pressure of 2 atm

Question 15

A gas sample contains 3.0 moles and occupies 67.2 L at STP. If the number of moles is doubled, what will be the new volume at STP?

Avogadro’s Law:
$$
\frac{V_1$}{n_1$} = \frac{V_2$}{n_2$}
$$

Accepted Answer

134.4 L

Question 16

Which of the following is the correct molar mass for $$\mathrm{Li_2CO_3}$$?

(Li: 6.94 g/mol, C: 12.01 g/mol, O: 16.00 g/mol)
$$
	ext{Molar mass} = (2 	imes 6.94) + (1 	imes 12.01) + (3 	imes 16.00)
$$

Accepted Answer

73.89 g/mol

Question 17

A deep-sea diver uses a gas mixture with a total pressure of 8.00 atm. If the oxygen partial pressure is 1280 mmHg, what is the partial pressure of helium? (1 atm = 760 mmHg)

Dalton’s Law:
$$
P_{	ext{total}} = P$$_{	ext{O}$$_2} + P_{	ext{He}}
$$

Accepted Answer

6.32 atm

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

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