Question 1

A weather report states the barometric pressure is 30.44 in Hg. What is this pressure in psi? (Given: $$1 \ 	ext{atm} = 14.7 \ 	ext{psi}$$, $$1 \ 	ext{atm} = 29.92 \ 	ext{in Hg})$$

Accepted Answer

$$14.96 \ 	ext{psi}$$

Question 2

A scuba diver takes a syringe filled with 16 mL of air from the surface (1.0 atm) to a depth where the volume is 7.5 mL. What is the pressure at this depth? (Assume temperature is constant.)

Accepted Answer

$$2.1 \ 	ext{atm}$$

Question 3

A gas sample has a volume of 2.80 L at an unknown temperature. When cooled in ice water ($$0^\circC$$), its volume decreases to 2.57 L. What was the initial temperature in Kelvin?

Accepted Answer

$$318 \ 	ext{K}$$

Question 4

A male athlete has a lung volume of 6.15 L during deep inhalation, containing 0.254 mol of air. After exhalation, his lung volume is 2.55 L. How many moles of air did he exhale? (Assume constant T and P.)

Accepted Answer

$$0.104 \ 	ext{mol}$$

Question 5

Calculate the volume occupied by 0.845 mol of nitrogen gas at a pressure of 1.37 atm and a temperature of 315 K. ($$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$15.9 \ 	ext{L}$$

Question 6

A 3.24-L basketball is inflated to a total pressure of 24.3 psi at 298 K. How many moles of gas are in the basketball? ($$1 \ 	ext{atm} = 14.7 \ 	ext{psi}$$, $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$0.219 \ 	ext{mol}$$

Question 7

Calculate the density of nitrogen gas at $$298 \ 	ext{K}$$ and a pressure of 755 mm Hg. ($$M_{N_2$} = 28.02 \ 	ext{g/mol}$$, $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$1 \ 	ext{atm} = 760 \ 	ext{mm Hg})$$

Accepted Answer

$$0.852 \ 	ext{g/L}$$

Question 8

A sample of gas has a mass of 0.311 g, a volume of 0.225 L, a temperature of 298 K, and a pressure of 886 mm Hg. What is its molar mass? ($$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$1 \ 	ext{atm} = 760 \ 	ext{mm Hg})$$

Accepted Answer

$$31.9 \ 	ext{g/mol}$$

Question 9

A 1.00-L mixture of helium, neon, and argon has a total pressure of 662 mm Hg at 298 K. If the partial pressures of helium and neon are 341 mm Hg and 112 mm Hg, respectively, what is the partial pressure of argon?

Accepted Answer

$$209 \ 	ext{mm Hg}$$

Question 10

A scuba tank contains a mixture of 24.2 g He and 4.32 g O$$_2 in a 12.5-L $$tank at 298 K. What is the mole fraction of oxygen in the mixture? ($$M_{He} = 4.00 \ 	ext{g/mol}$$, $$M_{O_2$} = 32.00 \ 	ext{g/mol})$$

Accepted Answer

$$0.112$$

Question 11

Oxygen gas is collected over water at 293 K and a total pressure of 755.2 mm Hg. If the vapor pressure of water at 293 K is 17.5 mm Hg, what is the partial pressure of oxygen?

Accepted Answer

$$737.7 \ 	ext{mm Hg}$$

Question 12

Methanol ($$CH_3OH) $$can be synthesized by the reaction: $$CO(g) + 2H_2(g) ightarrow CH_3OH(g). $$What volume of $$H_2$$ gas at 355 K and 738 mm Hg is needed to synthesize 35.7 g of methanol? ($$M_{CH_3OH} = 32.04 \ 	ext{g/mol}$$, $$R = 0.0821 \ 	ext{L} \cdot 	ext{atm} / 	ext{mol} \cdot 	ext{K}$$, $$1 \ 	ext{atm} = 760 \ 	ext{mm Hg})$$

Accepted Answer

$$66.9 \ 	ext{L}$$

Question 13

How many grams of water form when 1.24 L of $$H_2$$ gas at STP completely reacts with $$O_2$$? ($$M_{H_2O} = 18.02 \ 	ext{g/mol}$$, $$1 \ 	ext{mol}$$ gas at STP $$= 22.4 \ 	ext{L})$$

Accepted Answer

$$0.998 \ 	ext{g}$$

Question 14

Calculate the root mean square velocity of oxygen molecules at 298 K. ($$M_{O_2$} = 32.00 \ 	ext{g/mol}$$, $$R = 8.314 \ 	ext{J} / 	ext{mol} \cdot 	ext{K}$$, $$u_{rms} = \sqrt{\frac{3RT}{M}}$$, $$M in kg/$$mol)

Accepted Answer

$$482 \ 	ext{m/s}$$

Question 15

An unknown gas effuses at a rate that is 0.462 times that of nitrogen gas (at the same temperature). What is the molar mass of the unknown gas? ($$M_{N_2$} = 28.0 \ 	ext{g/mol}$$, $$\frac{	ext{rate}_1}{	ext{rate}_2} = \sqrt{\frac{M_2$}{M_1$}})$$

Accepted Answer

$$131 \ 	ext{g/mol}$$

Question 16

A sample of hydrogen gas is mixed with water vapor. The mixture has a total pressure of 755 torr, and the water vapor has a partial pressure of 24 torr. What is the partial pressure of hydrogen gas?

Accepted Answer

$$731 \ 	ext{torr}$$

Question 17

Which of the following statements best explains why the density of a gas decreases as temperature increases (at constant pressure)?

Accepted Answer

The gas molecules move faster and occupy a larger volume, decreasing density.

Chapter 6: Gases – General Chemistry Study Notes

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