Q: Which of the following is the correct value for the universal gas constant $$R$$ when pressure is in atm and volume in liters?

$$R = 0.0821\ \text{L} \cdot \text{atm} / \text{mol} \cdot \text{K}$$

Q: A sample of hydrogen gas is collected over water at 25°C. The total pressure is 755 mmHg and the vapor pressure of water at 25°C is 23.8 mmHg. What is the pressure of the dry hydrogen gas?

$$P_{\text{H}_2$$} = 755\ \text{mmHg} - 23.8\ \text{mmHg} = 731.2\ \text{mmHg}$$

Q: A 2.00 L sample of nitrogen gas at 1.00 atm and 273 K is heated to 546 K at constant pressure. What is the final volume?

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 2.00\ \text{L} \times \frac{546}{273} = 4.00\ \text{L}$$

Question 1

Which of the following statements is NOT a postulate of the Kinetic Molecular Theory of Gases?

Accepted Answer

Gas particles exert attractive forces on each other.

Question 2

A sample of gas occupies 2.50 L at 300 K and 1.00 atm. What will be its volume at 350 K and 2.00 atm?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$ $$T_2$$}{$$T_1$$ $$P_2$$} = \frac{(1.00\ 	ext{atm})(2.50\ 	ext{L})(350\ 	ext{K})}{(300\ 	ext{K})(2.00\ 	ext{atm})} = 1.46\ 	ext{L}$$

Question 3

Which of the following best explains why gases are compressible but solids are not?

Accepted Answer

Gas particles are far apart compared to their size, while solid particles are closely packed.

Question 4

A weather balloon is filled with 5.00 L of helium at 1.00 atm and 298 K. If the balloon rises to a region where the pressure is 0.500 atm and the temperature is 250 K, what will be the new volume of the balloon?

Accepted Answer

$$V_2$$ = \frac{$$P_1$$ $$V_1$$ $$T_2$$}{$$T_1$$ $$P_2$$} = \frac{(1.00)(5.00)(250)}{(298)(0.500)} = 8.39\ 	ext{L}$$

Question 5

Which of the following is the correct value for the universal gas constant $$R$$ when pressure is in atm and volume in liters?

Accepted Answer

$$R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$

Question 6

A 0.500 mol sample of oxygen gas is confined in a 10.0 L container at 27°C. What is the pressure of the gas? $$(R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{(0.500)(0.0821)(300)}{10.0} = 1.23\ 	ext{atm}$$

Question 7

Which of the following changes will increase the pressure of a fixed amount of gas in a rigid container?

Accepted Answer

Increasing the temperature of the gas.

Question 8

A sample of hydrogen gas is collected over water at 25°C. The total pressure is 755 mmHg and the vapor pressure of water at 25°C is 23.8 mmHg. What is the pressure of the dry hydrogen gas?

Accepted Answer

$$P_{	ext{H}_2$$} = 755\ 	ext{mmHg} - 23.8\ 	ext{mmHg} = 731.2\ 	ext{mmHg}$$

Question 9

Which of the following best describes the relationship between the volume and temperature of a gas at constant pressure?

Accepted Answer

The volume of a gas is directly proportional to its absolute temperature (in Kelvin).

Question 10

A 2.00 L sample of nitrogen gas at 1.00 atm and 273 K is heated to 546 K at constant pressure. What is the final volume?

Accepted Answer

$$V_2$$ = $$V_1$$ \frac{$$T_2$$}{$$T_1$$} = 2.00\ 	ext{L} 	imes \frac{546}{273} = 4.00\ 	ext{L}$$

Question 11

Which of the following is NOT a correct statement about STP (Standard Temperature and Pressure)?

Accepted Answer

STP is defined as 25°C (298 K) and 1 atm pressure.

Question 12

A sample of gas has a pressure of 2.00 atm, a volume of 4.00 L, and a temperature of 300 K. What is the number of moles of gas present? $$(R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$n = \frac{PV}{RT} = \frac{(2.00)(4.00)}{(0.0821)(300)} = 0.324\ 	ext{mol}$$

Question 13

Which of the following is the correct mathematical expression for Boyle's Law?

Accepted Answer

$$P_1$$ $$V_1$$ = $$P_2$$ $$V_2$$

Question 14

A 1.00 L flask contains 0.0400 mol of a gas at 300 K. What is the pressure in the flask? $$(R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{(0.0400)(0.0821)(300)}{1.00} = 0.985\ 	ext{atm}$$

Question 15

Which of the following is a real-world application of Dalton's Law of Partial Pressures?

Accepted Answer

Collecting a gas over water in the laboratory.

Question 16

A 2.00 L container holds 0.100 mol of neon gas at 27°C. What is the pressure inside the container? $$(R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{(0.100)(0.0821)(300)}{2.00} = 1.23\ 	ext{atm}$$

Question 17

Which of the following statements about the behavior of real gases is correct?

Accepted Answer

Real gases deviate from ideal behavior at high pressures and low temperatures.

Question 18

A gas sample has a mass of 4.00 g and occupies 2.00 L at 1.00 atm and 273 K. What is the molar mass of the gas? $$(R = 0.0821\ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$n = \frac{PV}{RT} = \frac{(1.00)(2.00)}{(0.0821)(273)} = 0.0895\ 	ext{mol}$$; Molar\ Mass = \frac{4.00\ 	ext{g}}{0.0895\ 	ext{mol}} = 44.7\ 	ext{g/mol}$

Study Notes: Chapter 11 – Gases (CHMI032 Pre-Test 4)

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