Q: A gas has a pressure of 2.0 atm at 18°C. What is the new pressure when the temperature is increased to 62°C, assuming constant volume and moles?

$$P_2$$ = \frac{T_2P_1}{$$T_1$$} = \frac{335\,K \times 2.0\,atm}{291\,K} = 2.3\,atm$$

Q: A 20.0-L tank contains 2.86 mol of $$N_2O at 23$$°C. What is the pressure in the tank? ($$R = 0.0821\,L\cdot atm/(mol\cdot K))$$

$$P = \frac{nRT}{V} = \frac{2.86\,mol \times 0.0821\,L\cdot atm/(mol\cdot K) \times 296\,K}{20.0\,L} = 3.48\,atm$$

Q: 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?

$$T_2$$ = \frac{P_2V_2T_1}{P_1V_1} = \frac{3.20\,atm \times 0.0900\,L \times 302\,K}{0.800\,atm \times 0.180\,L} = 604\,K = 331^\circ C$$

Q: If 0.75 mol of helium gas occupies a volume of 1.5 L, what volume will 1.2 mol of helium occupy at the same temperature and pressure?

$$V_2$$ = \frac{n_2V_1}{$$n_1$$} = \frac{1.2\,mol \times 1.5\,L}{0.75\,mol} = 2.4\,L$$

Q: A gas has a volume of 675 mL at 35°C and 0.850 atm. What is the volume at -95°C and 802 mmHg? ($$1\,atm = 760\,mmHg)$$

$$V_2$$ = \frac{P_1V_1T_2}{P_2T_1} = \frac{0.850\,atm \times 675\,mL \times 178\,K}{1.06\,atm \times 308\,K} = 314\,mL$$

Question 1

A sample of helium gas in a balloon has a volume of 6.4 L at a pressure of 0.70 atm. If the pressure is increased to 1.40 atm at constant temperature, what will happen to the volume of the balloon?

Accepted Answer

The volume will decrease to half its original value.

Question 2

Which equation correctly represents Boyle’s Law?

Accepted Answer

$$P_1V_1 = P_2V_2$$

Question 3

A balloon filled with air at room temperature is placed in a freezer. Which of the following best explains what happens to the balloon?

Accepted Answer

The balloon shrinks because the volume of a gas decreases as temperature decreases (Charles’s Law).

Question 4

A gas has a pressure of 2.0 atm at 18°C. What is the new pressure when the temperature is increased to 62°C, assuming constant volume and moles?

Accepted Answer

$$P_2$$ = \frac{T_2P_1}{$$T_1$$} = \frac{335\,K 	imes 2.0\,atm}{291\,K} = 2.3\,atm$$

Question 5

Which of the following statements about ideal and real gases is correct?

Accepted Answer

Real gases deviate from ideal behavior at high pressures and low temperatures due to intermolecular forces.

Question 6

A 20.0-L tank contains 2.86 mol of $$N_2O at 23$$°C. What is the pressure in the tank? ($$R = 0.0821\,L\cdot atm/(mol\cdot K))$$

Accepted Answer

$$P = \frac{nRT}{V} = \frac{2.86\,mol 	imes 0.0821\,L\cdot atm/(mol\cdot K) 	imes 296\,K}{20.0\,L} = 3.48\,atm$$

Question 7

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?

Accepted Answer

$$T_2$$ = \frac{P_2V_2T_1}{P_1V_1} = \frac{3.20\,atm 	imes 0.0900\,L 	imes 302\,K}{0.800\,atm 	imes 0.180\,L} = 604\,K = 331^\circ C$$

Question 8

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

Accepted Answer

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

Question 9

A Heliox breathing mixture for a scuba diver at 7.00 atm total pressure contains oxygen at a partial pressure of 1140 mmHg. What is the partial pressure of helium in atm? ($$1\,atm = 760\,mmHg)$$

Accepted Answer

$$P_{He} = P_{total} - P_{O_2$} = 7.00\,atm - 1.50\,atm = 5.50\,atm$$

Question 10

If 0.75 mol of helium gas occupies a volume of 1.5 L, what volume will 1.2 mol of helium occupy at the same temperature and pressure?

Accepted Answer

$$V_2$$ = \frac{n_2V_1}{$$n_1$$} = \frac{1.2\,mol 	imes 1.5\,L}{0.75\,mol} = 2.4\,L$$

Question 11

A gas has a volume of 675 mL at 35°C and 0.850 atm. What is the volume at -95°C and 802 mmHg? ($$1\,atm = 760\,mmHg)$$

Accepted Answer

$$V_2$$ = \frac{P_1V_1T_2}{P_2T_1} = \frac{0.850\,atm 	imes 675\,mL 	imes 178\,K}{1.06\,atm 	imes 308\,K} = 314\,mL$$

Question 12

Which of the following is the correct value for the gas constant $$R in $$the ideal gas law $$PV = nRT$$ when pressure is in atm and volume is in liters?

Accepted Answer

$$0.0821\,L\cdot atm/(mol\cdot K)$$

Question 13

Which of the following best describes the relationship between temperature and kinetic energy of gas particles?

Accepted Answer

Kinetic energy increases as Kelvin temperature increases.

Question 14

A balloon contains 785 mL of gas at 21°C. If the temperature drops to 0°C at constant pressure, what is the new volume?

Accepted Answer

$$V_2$$ = \frac{V_1T_2}{$$T_1$$} = \frac{785\,mL 	imes 273\,K}{294\,K} = 729\,mL$$

Question 15

Which of the following is NOT a property used to describe gases?

Accepted Answer

Color

Chapter 8: Gases – Fundamental Properties and Laws

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