Q: A sample of gas occupies 2.90 L at an unknown temperature. When submerged in ice water, its volume decreases to 2.50 L. If the initial pressure is constant, what was the initial temperature in Kelvin?

$$T_1$$ = \frac{$$V_1$$}{$$V_2$$} \times $$T_2$$ = \frac{2.90}{2.50} \times 273.15 \approx 317.5\ \text{K}$$

Q: A gas sample has a mass of 0.311 g and occupies 0.225 L at a pressure of 886 mmHg and a temperature of 55°C. What is the molar mass of the gas?

$$M = \frac{mRT}{PV} = \frac{0.311 \times 0.08206 \times 328.15}{(886/760) \times 0.225} \approx 44.0\ \text{g/mol}$$

Q: At STP, what is the density of nitrogen gas ($$N_2$$)?

$$d = \frac{\text{molar mass}}{\text{molar volume}} = \frac{28.02\ \text{g/mol}}{22.4\ \text{L/mol}} = 1.25\ \text{g/L}$$

Q: A cylinder contains 0.62 mol of gas at a certain volume. After a reaction, the cylinder contains 0.20 mol of gas and the volume is 2.13 L. Assuming constant pressure and temperature, what was the initial volume?

$$V_1$$ = \frac{$$n_1$$}{$$n_2$$} \times $$V_2$$ = \frac{0.62}{0.20} \times 2.13 = 6.61\ \text{L}$$

Question 1

Which statement best explains why gases are compressible, while liquids and solids are not?

Accepted Answer

Gases have particles that are much farther apart compared to liquids and solids, allowing them to be compressed.

Question 2

According to the kinetic molecular theory, which of the following is NOT an assumption made about ideal gases?

Accepted Answer

Gas particles interact with each other through strong attractive forces.

Question 3

A diver descends to a depth where the pressure is 3 atm. If the diver holds their breath and ascends rapidly to the surface (1 atm), what happens to the volume of air in their lungs according to Boyle's Law?

Accepted Answer

The volume of air in the lungs will expand by a factor of 3.

Question 4

Which equation correctly represents the relationship between pressure and volume for a fixed amount of gas at constant temperature (Boyle's Law)?

Accepted Answer

$$P V = 	ext{constant}$$

Question 5

A sample of gas occupies 2.90 L at an unknown temperature. When submerged in ice water, its volume decreases to 2.50 L. If the initial pressure is constant, what was the initial temperature in Kelvin?

Accepted Answer

$$T_1$$ = \frac{$$V_1$$}{$$V_2$$} 	imes $$T_2$$ = \frac{2.90}{2.50} 	imes 273.15 \approx 317.5\ 	ext{K}$$

Question 6

Which of the following best describes Graham's Law of Effusion?

Accepted Answer

The rate of effusion of a gas is inversely proportional to the square root of its molar mass.

Question 7

A gas sample has a mass of 0.311 g and occupies 0.225 L at a pressure of 886 mmHg and a temperature of 55°C. What is the molar mass of the gas?

Accepted Answer

$$M = \frac{mRT}{PV} = \frac{0.311 	imes 0.08206 	imes 328.15}{(886/760) 	imes 0.225} \approx 44.0\ 	ext{g/mol}$$

Question 8

Which of the following is the correct formula for the root-mean-square speed ($$u_{rms}) of a $$gas molecule?

Accepted Answer

$$u_{rms} = \sqrt{\frac{3RT}{M}}$$

Question 9

At STP, what is the density of nitrogen gas ($$N_2$$)?

Accepted Answer

$$d = \frac{	ext{molar mass}}{	ext{molar volume}} = \frac{28.02\ 	ext{g/mol}}{22.4\ 	ext{L/mol}} = 1.25\ 	ext{g/L}$$

Question 10

Which of the following statements about diffusion and effusion is correct?

Accepted Answer

Diffusion is the spread of one substance through another, while effusion is the escape of gas particles through a tiny hole.

Question 11

A cylinder contains 0.62 mol of gas at a certain volume. After a reaction, the cylinder contains 0.20 mol of gas and the volume is 2.13 L. Assuming constant pressure and temperature, what was the initial volume?

Accepted Answer

$$V_1$$ = \frac{$$n_1$$}{$$n_2$$} 	imes $$V_2$$ = \frac{0.62}{0.20} 	imes 2.13 = 6.61\ 	ext{L}$$

Question 12

Which of the following is the correct form of the ideal gas law?

Accepted Answer

$$PV = nRT$$

Question 13

A sample contains 0.845 mol of $$SO_2$$ gas at a volume of 15.9 L and a temperature of 305 K. What is the pressure in atm?

Accepted Answer

$$P = \frac{nRT}{V} = \frac{0.845 	imes 0.08206 	imes 305}{15.9} \approx 1.33\ 	ext{atm}$$

Question 14

Which of the following is true about the average kinetic energy of gas particles?

Accepted Answer

It is directly proportional to the absolute temperature.

Question 15

Which pressure unit is equivalent to 1 atm?

Accepted Answer

760 mmHg

Question 16

If the temperature of a gas is doubled at constant pressure, what happens to its volume?

Accepted Answer

The volume doubles.

Question 17

Which of the following gases will effuse the fastest under identical conditions?

Accepted Answer

Helium ($$He)$$

Question 18

A sample of hydrogen gas has a density of 0.179 g/L at STP. What is the molar mass of hydrogen?

Accepted Answer

$$M = d 	imes 	ext{molar volume} = 0.179 	imes 22.4 = 4.01\ 	ext{g/mol}$$

lecture slides chapter 9

Study Guide - Practice Questions

Study Guide - Flashcards