Question 1

How many moles of a gas at $$100\ ^\circ\mathrm{C}$$ does it take to fill a $$1.00\ \mathrm{L}$$ flask to a pressure of $$1.50\ \mathrm{atm}$$? Use $$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)}.$$

Accepted Answer

$$0.061\ \mathrm{mol}$$

Question 2

A camping stove holds $$3000.0\ \mathrm{g} of $$liquid $$\mathrm{C}_5\mathrm{H}_{12}. $$How large of a container would be needed to hold the gas at a temperature of $$25\ ^\circ\mathrm{C}$$ and a pressure of $$3.0\ \mathrm{atm}$$? (Molar mass of $$\mathrm{C}_5\mathrm{H}_{12} = 72.15\ \mathrm{g/mol})$$

Accepted Answer

$$33,900\ \mathrm{L}$$

Question 3

A $$10.0\ \mathrm{L}$$ gas cylinder contains $$55$$ moles of nitrogen. What pressure, in kPa, is exerted by the nitrogen at $$25\ ^\circ\mathrm{C}$$? ($$R = 8.314\ \mathrm{L\cdot kPa/(mol\cdot K)})$$

Accepted Answer

$$1,370\ \mathrm{kPa}$$

Question 4

A drum used to transport crude oil has a volume of $$162\ \mathrm{L}. $$How many grams of water, as steam, are required to fill the drum at $$1.20\ \mathrm{atm}$$ and $$100.0\ ^\circ\mathrm{C}$$? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)}$$; $$M_{\mathrm{H}_2$$\mathrm{O}} = 18.02\ \mathrm{g/mol}$$)

Accepted Answer

$$1,180\ \mathrm{g}$$

Question 5

If you have a gas at a pressure of $$12\ \mathrm{atm}$$, a volume of $$23\ \mathrm{L}$$, and a temperature of $$200.0\ \mathrm{K}$$, and then you raise the pressure to $$14\ \mathrm{atm}$$ and increase the temperature to $$300.0\ \mathrm{K}$$, what is the new volume of the gas?

Accepted Answer

$$29.5\ \mathrm{L}$$

Question 6

A gas has a volume of $$28\ \mathrm{L}$$, a temperature of $$45^\circ\mathrm{C}$$, and an unknown pressure. Its volume increases to $$34\ \mathrm{L}$$ and its temperature decreases to $$35^\circ\mathrm{C}. If $$you measure the pressure after the change to be $$2.0\ \mathrm{atm}$$, what was the original pressure of the gas?

Accepted Answer

$$2.7\ \mathrm{atm}$$

Question 7

What is the density of a gas with molar mass $$100\ \mathrm{g/mol} at$$ $$0.5\ \mathrm{atm}$$ and $$27^\circ\mathrm{C}$$? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$1.98\ \mathrm{g/L}$$

Question 8

You have $$6.3\ \mathrm{mg} of a $$boron hydride in a flask of $$385\ \mathrm{mL} at$$ $$25.0^\circ\mathrm{C}$$ and a pressure of $$11\ \mathrm{torr}$$. ($$R = 62.4\ \mathrm{L\cdot torr/(mol\cdot K)}) $$What is the molar mass of the hydride?

Accepted Answer

$$36\ \mathrm{g/mol}$$

Question 9

Given the molar mass calculated in the previous question, which of the following hydrides is contained in the flask: $$\mathrm{BH}_3$$, $$\mathrm{B}_2\mathrm{H}_6$$, or $$\mathrm{B}_4\mathrm{H}_{10}$$?

Accepted Answer

$$\mathrm{B}_2\mathrm{H}_6$$

Question 10

Calculate the partial pressure of $$\mathrm{O}_2 in $$the air outside an airplane cruising at an altitude of $$10\ \mathrm{km}$$, where the atmospheric pressure is $$190.0\ \mathrm{torr}. $$The mole fraction of $$\mathrm{O}_2 in $$the air is $$0.210.$$

Accepted Answer

$$39.9\ \mathrm{torr}$$

Question 11

A gas mixture called Trimix that is $$11.7\% He$$, $$56.2\% N$_2$$, and $$32.1\% O$_2 is $$used in scuba tanks to avoid nitrogen narcosis at great depth. What is the mole fraction of He in this mixture?

Accepted Answer

$$0.117$$

Question 12

Which of the following changes will increase the density of a gas, assuming the amount of gas remains constant?

Accepted Answer

Decreasing the temperature while keeping the pressure constant

Question 13

A scuba diver uses a $$12.0\ \mathrm{L}$$ tank filled with air at $$200\ \mathrm{atm}$$ and $$27^\circ\mathrm{C}. $$How many moles of air are in the tank? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$96.0\ \mathrm{mol}$$

Question 14

A $$5.00\ \mathrm{g}$$ sample of an unknown gas occupies $$2.50\ \mathrm{L} at$$ $$1.00\ \mathrm{atm}$$ and $$27^\circ\mathrm{C}. $$What is the molar mass of the gas?

Accepted Answer

$$48.8\ \mathrm{g/mol}$$

Question 15

A weather balloon is filled with $$15.0\ \mathrm{L} of $$helium at $$1.00\ \mathrm{atm}$$ and $$20^\circ\mathrm{C}. If $$the balloon rises to an altitude where the pressure is $$0.600\ \mathrm{atm}$$ and the temperature is $$-10^\circ\mathrm{C}$$, what is the new volume of the balloon?

Accepted Answer

$$23.7\ \mathrm{L}$$

Question 16

A $$2.00\ \mathrm{L}$$ flask contains a mixture of $$0.50\ \mathrm{mol} of$$ $$\mathrm{O}_2$$ and $$0.30\ \mathrm{mol} of$$ $$\mathrm{N}_2 at$$ $$27^\circ\mathrm{C}. $$What is the total pressure in the flask? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$9.8\ \mathrm{atm}$$

Question 17

A $$1.00\ \mathrm{L}$$ flask contains $$0.040\ \mathrm{mol} of$$ $$\mathrm{CO}_2 at$$ $$27^\circ\mathrm{C}. $$What is the pressure in the flask? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$0.98\ \mathrm{atm}$$

Question 18

A $$10.0\ \mathrm{g}$$ sample of methane ($$\mathrm{CH}_4) is $$burned in excess oxygen. What volume of $$\mathrm{CO}_2$$ gas is produced at $$1.00\ \mathrm{atm}$$ and $$273\ \mathrm{K}$$? ($$M_{\mathrm{CH}_4$$} = 16.0\ \mathrm{g/mol}$$; 1$$\ \mathrm{mol}$$ gas at STP = 22.4$$\ \mathrm{L}$$)

Accepted Answer

$$14.0\ \mathrm{L}$$

Question 19

A $$3.00\ \mathrm{L}$$ container holds $$0.10\ \mathrm{mol} of$$ $$\mathrm{O}_2$$ and $$0.20\ \mathrm{mol} of$$ $$\mathrm{CO}_2 at$$ $$27^\circ\mathrm{C}. $$What is the partial pressure of $$\mathrm{CO}_2 in $$the container? ($$R = 0.0821\ \mathrm{L\cdot atm/(mol\cdot K)})$$

Accepted Answer

$$1.63\ \mathrm{atm}$$

Chapter 10: Gases – The Ideal Gas Law, Gas Properties, and Mixtures

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