# 7.3.1: Practice Problems- Applications of the Ideal Gas Law

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PROBLEM \(\PageIndex{1}\)

What is the density of laughing gas, dinitrogen monoxide, N_{2}O, at a temperature of 325 K and a pressure of 113.0 kPa?

**Answer**-
1.84 g/L

PROBLEM \(\PageIndex{2}\)

Calculate the density of Freon 12, CF_{2}Cl_{2}, at 30.0 °C and 0.954 atm.

**Answer**-
4.64 g/L

**Click here to see a video of the solution**-

PROBLEM \(\PageIndex{3}\)

Which is denser at the same temperature and pressure, dry air or air saturated with water vapor? Explain.

**Answer**-
air saturated with water vapor - it has a higher molar mass

PROBLEM \(\PageIndex{4}\)

A cylinder of O_{2}(*g*) used in breathing by emphysema patients has a volume of 3.00 L at a pressure of 10.0 atm. If the temperature of the cylinder is 28.0 °C, what mass of oxygen is in the cylinder?

**Answer**-
38.8 g

**Click here to see a video of the solution**-

PROBLEM \(\PageIndex{5}\)

What is the molar mass of a gas if 0.0494 g of the gas occupies a volume of 0.100 L at a temperature 26 °C and a pressure of 307 torr?

**Answer**-
30.0 g/mol

PROBLEM \(\PageIndex{6}\)

What is the molar mass of a gas if 0.281 g of the gas occupies a volume of 125 mL at a temperature 126 °C and a pressure of 777 torr?

**Answer**-
72.0 g/mol

**Click here to see a video of the solution**-

PROBLEM \(\PageIndex{7}\)

The density of a certain gaseous fluoride of phosphorus is 3.93 g/L at STP. Calculate the molar mass of this fluoride and determine its molecular formula.

**Answer**-
88.1 g mol

^{−1}; PF_{3}

PROBLEM \(\PageIndex{8}\)

What is the molecular formula of a compound that contains 39% C, 45% N, and 16% H if 0.157 g of the compound occupies 125 mL with a pressure of 99.5 kPa at 22 °C?

**Answer**-
H

_{5}CN

**Click here to see a video of the solution**-

PROBLEM \(\PageIndex{9}\)

A sample of gas isolated from unrefined petroleum contains 90.0% CH_{4}, 8.9% C_{2}H_{6}, and 1.1% C_{3}H_{8} at a total pressure of 307.2 kPa. What is the partial pressure of each component of this gas? (The percentages given indicate the percent of the total pressure that is due to each component.)

**Answer**-
CH

_{4}: 276 kPa; C_{2}H_{6}: 27 kPa; C_{3}H_{8}: 3.4 kPa

PROBLEM \(\PageIndex{10}\)

Automobile air bags are inflated with nitrogen gas, which is formed by the decomposition of solid sodium azide (NaN_{3}). The other product is sodium metal. Calculate the volume of nitrogen gas at 27 °C and 756 torr formed by the decomposition of 125 g of sodium azide.

**Answer**-
71.26 L

**Click here to see a video of the solution**-

PROBLEM \(\PageIndex{11}\)

A sample of a compound of xenon and fluorine was confined in a bulb with a pressure of 18 torr. Hydrogen was added to the bulb until the pressure was 72 torr. Passage of an electric spark through the mixture produced Xe and HF. After the HF was removed by reaction with solid KOH, the final pressure of xenon and unreacted hydrogen in the bulb was 36 torr. What is the empirical formula of the xenon fluoride in the original sample? (Note: Xenon fluorides contain only one xenon atom per molecule.)

**Answer**-
XeF

_{2}

## Contributors

Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).

- Adelaide Clark, Oregon Institute of Technology