Q: According to Avogadro’s Law, if a weather balloon with a volume of 44 L is filled with 2.0 moles of helium, what will be the final volume if 3.0 moles of helium are added (for a total of 5.0 moles)?

$$V_2$$ = $$V_1$$ \times \frac{$$n_2$$}{$$n_1$$} = 44 \times \frac{5.0}{2.0} = 110\ \text{L}$$

Q: What is the volume at STP of 4.0 moles of methane ($$\mathrm{CH_4$}$$)?

$$V = 4.0 \times 22.4 = 89.6\ \text{L}$$

Q: A scuba diver uses a mixture of helium and oxygen with a total pressure of 8.00 atm. If the oxygen has a partial pressure of 1280 mmHg, what is the partial pressure of the helium? (1 atm = 760 mmHg)

$$P_{\text{He}} = 8.00\ \text{atm} - \frac{1280}{760}\ \text{atm} = 6.32\ \text{atm}$$

Q: Which of the following statements best describes the meaning of STP in gas law calculations?

STP refers to a temperature of $$273\ \text{K}$$ and a pressure of $$1\ \text{atm}.$$

Q: A 2.0 L sample of nitrogen gas at 1.0 atm and 273 K is compressed to 1.0 L at constant temperature. What is the new pressure?

$$P_2$$ = \frac{$$P_1$$ $$V_1$$}{$$V_2$$} = \frac{1.0 \times 2.0}{1.0} = 2.0\ \text{atm}$$

Q: A 5.0 L container holds 2.0 moles of oxygen gas at STP. What would be the volume if the amount of gas is increased to 4.0 moles, with temperature and pressure constant?

$$V_2 = 5.0$$ \times \frac{4.0}{2.0} = 10.0\ \text{L}$$

Q: Which of the following is true about the molar volume of a gas at STP?

One mole of any ideal gas occupies $$22.4\ \text{L} at $$STP.

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

$$P_{\text{total}} = 2.0 + 1.0 + 0.5 = 3.5\ \text{atm}$$

Question 1

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

Accepted Answer

$$T_2$$ = \frac{$$P_2$$ $$V_2$$ $$T_1$$}{$$P_1$$ $$V_1$$} = \frac{3.20 	imes 0.0900 	imes 302}{0.800 	imes 0.180} = 604\ 	ext{K} ightarrow 331\ ^\circ	ext{C}$$

Question 2

According to Avogadro’s Law, if a weather balloon with a volume of 44 L is filled with 2.0 moles of helium, what will be the final volume if 3.0 moles of helium are added (for a total of 5.0 moles)?

Accepted Answer

$$V_2$$ = $$V_1$$ 	imes \frac{$$n_2$$}{$$n_1$$} = 44 	imes \frac{5.0}{2.0} = 110\ 	ext{L}$$

Question 3

What is the volume at STP of 4.0 moles of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

$$V = 4.0 	imes 22.4 = 89.6\ 	ext{L}$$

Question 4

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

Accepted Answer

$$P_{	ext{He}} = 8.00\ 	ext{atm} - \frac{1280}{760}\ 	ext{atm} = 6.32\ 	ext{atm}$$

Question 5

Which of the following statements best describes the meaning of STP in gas law calculations?

Accepted Answer

STP refers to a temperature of $$273\ 	ext{K}$$ and a pressure of $$1\ 	ext{atm}.$$

Question 6

If the pressure of a gas is doubled while the temperature and amount of gas remain constant, what happens to the volume according to the Combined Gas Law?

Accepted Answer

The volume is halved.

Question 7

A 2.0 L sample of nitrogen gas at 1.0 atm and 273 K is compressed to 1.0 L at constant temperature. What is the new pressure?

Accepted Answer

$$P_2$$ = \frac{$$P_1$$ $$V_1$$}{$$V_2$$} = \frac{1.0 	imes 2.0}{1.0} = 2.0\ 	ext{atm}$$

Question 8

Which law states that the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases?

Accepted Answer

Dalton’s Law of Partial Pressures

Question 9

A 5.0 L container holds 2.0 moles of oxygen gas at STP. What would be the volume if the amount of gas is increased to 4.0 moles, with temperature and pressure constant?

Accepted Answer

$$V_2 = 5.0$$ 	imes \frac{4.0}{2.0} = 10.0\ 	ext{L}$$

Question 10

Which of the following is true about the molar volume of a gas at STP?

Accepted Answer

One mole of any ideal gas occupies $$22.4\ 	ext{L} at $$STP.

Question 11

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

Accepted Answer

$$P_{	ext{total}} = 2.0 + 1.0 + 0.5 = 3.5\ 	ext{atm}$$

Question 12

If you have 1 mole of helium, 1 mole of oxygen, and 1 mole of nitrogen each at STP, what is the volume of each gas?

Accepted Answer

$$22.4\ 	ext{L}$$

Question 13

A gas sample at 1.0 atm and 273 K occupies 22.4 L. If the pressure is increased to 2.0 atm at constant temperature, what is the new volume?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$}{$$P_2$$} = \frac{1.0 	imes 22.4}{2.0} = 11.2\ 	ext{L}$$

Question 14

Which of the following best explains why all gases have the same molar volume at STP?

Accepted Answer

Gas particles are far apart and the identity of the gas does not affect the volume at STP.

Question 15

A 10.0 L tank contains a mixture of gases at 300 K: 1.0 mole of He, 2.0 moles of O$$_2$$, and 3.0 moles of N$$_2. $$What is the total number of moles in the tank?

Accepted Answer

6.0 moles

Gas Laws: Combined, Avogadro’s, STP, and Dalton’s Law

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