Q: Which of the following is NOT a correct value for the gas constant $$R$$?

$$R = 1.00 \ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K}$$

Q: If a gas sample occupies 2.50 L at 190 $$^ ext{o}C $$and 1.20 atm, how many moles of gas are present? (Use $$R = 0.0821 \ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K})$$

$$n = \frac{P V}{R T} = \frac{1.20 \times 2.50}{0.0821 \times (190 + 273)}$$

Q: A 0.150 L flask contains CO$$_2 at 525 $$mmHg and 32 $$^ ext{o}C. $$What is the mass of CO$$_2 in $$the flask? (Molar mass of CO$$_2 = 44.0 g/$$mol, $$R = 62.4 \ \text{L} \cdot \text{mmHg} / \text{mol} \cdot \text{K})$$

$$m = n \times 44.0 = \frac{P V}{R T} \times 44.0$$

Q: A mixture of argon and oxygen is placed in a 500 mL container. If 0.073 g of argon is added and the total pressure is 1.52 atm at 342 K, what is the mass of oxygen present? (Molar mass of Ar = 40.0 g/mol, O$$_2 = 32.0 g/$$mol, $$R = 0.0821 \ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K})$$

Calculate $$n_{\text{Ar}}$$, subtract $$P_{\text{Ar}}$$ from total $$P$$, use $$P_{\text{O}_2$$}$$ to find n$$_{\text{O}$$_2}$$, then $$m_{\text{O}_2$$} = $$n_{\text{O}_2$$} \times 32.0$$

Q: A gas sample is collected at 780 torr and 28 $$^ ext{o}C. $$What is the pressure in atm?

$$P = \frac{780}{760} = 1.03 \ \text{atm}$$

Question 1

Which of the following correctly expresses the Ideal Gas Law equation?

Accepted Answer

$$P V = n R T$$

Question 2

A 500 mL container at a pressure of 600 mmHg contains 23.9 g of nitrogen gas at 50 $$^	ext{o}C. $$What is the value of $$n ($$number of moles) for the nitrogen gas?

Accepted Answer

$$n = \frac{23.9}{28.0} = 0.854$$

Question 3

Which of the following is NOT a correct value for the gas constant $$R$$?

Accepted Answer

$$R = 1.00 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$

Question 4

If a gas sample occupies 2.50 L at 190 $$^	ext{o}C $$and 1.20 atm, how many moles of gas are present? (Use $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$n = \frac{P V}{R T} = \frac{1.20 	imes 2.50}{0.0821 	imes (190 + 273)}$$

Question 5

A 0.150 L flask contains CO$$_2 at 525 $$mmHg and 32 $$^	ext{o}C. $$What is the mass of CO$$_2 in $$the flask? (Molar mass of CO$$_2 = 44.0 g/$$mol, $$R = 62.4 \ 	ext{L} \cdot 	ext{mmHg} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$m = n 	imes 44.0 = \frac{P V}{R T} 	imes 44.0$$

Question 6

Which of the following scenarios would require you to use the Ideal Gas Law rather than Boyle's or Charles's Law?

Accepted Answer

Calculating the number of moles of a gas given pressure, volume, and temperature.

Question 7

A mixture of argon and oxygen is placed in a 500 mL container. If 0.073 g of argon is added and the total pressure is 1.52 atm at 342 K, what is the mass of oxygen present? (Molar mass of Ar = 40.0 g/mol, O$$_2 = 32.0 g/$$mol, $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

Calculate $$n_{	ext{Ar}}$$, subtract $$P_{	ext{Ar}}$$ from total $$P$$, use $$P_{	ext{O}_2$$}$$ to find n$$_{	ext{O}$$_2}$$, then $$m_{	ext{O}_2$$} = $$n_{	ext{O}_2$$} 	imes 32.0$$

Question 8

Which of the following is a correct conversion for temperature when using the Ideal Gas Law?

Accepted Answer

Convert Celsius to Kelvin by adding 273

Question 9

A student measures 6.2 L of NO$$_2$$ gas at 28 $$^	ext{o}C $$and 780 torr. How many moles of NO$$_2$$ are present? ($$R = 62.4 \ 	ext{L} \cdot 	ext{mmHg} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$n = \frac{P V}{R T}$$

Question 10

Why is it important to use the correct value of $$R in $$the Ideal Gas Law calculations?

Accepted Answer

Because $$R$$ must match the units of pressure and volume used in the calculation.

Question 11

A gas sample is collected at 780 torr and 28 $$^	ext{o}C. $$What is the pressure in atm?

Accepted Answer

$$P = \frac{780}{760} = 1.03 \ 	ext{atm}$$

Question 12

Which of the following best describes the relationship between pressure and volume in the Ideal Gas Law?

Accepted Answer

Pressure and volume are inversely proportional when temperature and moles are constant.

Question 13

A 2.01 L solution of 4.15 M nitric acid is prepared using NO$$_2$$ gas at 28 $$^	ext{o}C $$and 780 torr. How many liters of NO$$_2$$ gas are required?

Accepted Answer

Calculate moles of HNO$$_3$$, use stoichiometry to find moles of NO$$_2$$, then use $$V = \frac{n R T}{P}$$

Question 14

Which of the following is a common mistake when using the Ideal Gas Law?

Accepted Answer

Using Celsius instead of Kelvin for temperature.

Question 15

If the pressure of a gas is doubled while temperature and moles remain constant, what happens to the volume?

Accepted Answer

The volume is halved.

The Ideal Gas Law and Gas Constant: Study Notes

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