CHEM 5013CHEM 5013

Applied Chemical Applied Chemical PrinciplesPrinciplesChapter FiveChapter Five

Professor BensleyProfessor BensleyAlfred State CollegeAlfred State College

Chapter ObjectivesChapter Objectives

Describe the physical properties of Describe the physical properties of gases.gases.

Use the ideal gas law for calculating Use the ideal gas law for calculating changes in the conditions of gases.changes in the conditions of gases.

Use the concept of partial pressure to Use the concept of partial pressure to work with mixtures of gases.work with mixtures of gases.

Perform stoichiometric calculations for Perform stoichiometric calculations for reactions involving gases as reactants reactions involving gases as reactants or products.or products.

Properties of GasesProperties of Gases

1.1.

2.2.

3.3.

4.4.

5.5.

PressurePressure Pressure:Pressure:

Gas Gas PressurePressure

Pressure is the Pressure is the result of molecular result of molecular collisions between collisions between gas molecules and gas molecules and container walls. container walls.

A barometer is A barometer is used to measure used to measure pressure.pressure.

Units of Pressure and STPUnits of Pressure and STP 1 torr = 1 mm Hg1 torr = 1 mm Hg 1 atm = 760 torr = 760 mm Hg (exactly)1 atm = 760 torr = 760 mm Hg (exactly) 1 atm = 101,325 Pa (exactly)1 atm = 101,325 Pa (exactly) 1 atm = 14.7 psi1 atm = 14.7 psi

At sea level, atmospheric pressure is? At sea level, atmospheric pressure is? Standard Temperature and Pressure Standard Temperature and Pressure

Conditions (STP):Conditions (STP):

Empirical Gas LawsEmpirical Gas Laws Gases behave simply under “moderate” Gases behave simply under “moderate”

conditions with respect to four things:conditions with respect to four things:1)1)

2)2)

3)3)

4)4)

Boyle’s LawBoyle’s Law

PV = constantPV = constant P P11VV11 = P = P22VV22 For a given amount of gas at a constant temp.For a given amount of gas at a constant temp.

Charles’s LawCharles’s Law

V/T = constantV/T = constant VV1 1 / T/ T11=V=V2 2 / T/ T22For a given amount of gas at a given pressureFor a given amount of gas at a given pressure

WARNING – Temperature must be absolute (Kelvin Units) for ALL WARNING – Temperature must be absolute (Kelvin Units) for ALL gas laws.gas laws.

ExamplesExamples A volume of oxygen gas occupies 38.7 mL at A volume of oxygen gas occupies 38.7 mL at

751 mm Hg at 21751 mm Hg at 21°C. What is the volume if °C. What is the volume if the pressure changes to 359 mm Hg and the pressure changes to 359 mm Hg and temp. remains constant?temp. remains constant?

You prepared carbon dioxide by adding You prepared carbon dioxide by adding HCl(aq) to marble chips (CaCOHCl(aq) to marble chips (CaCO33). According ). According to your calculations, you should obtain 79.4 to your calculations, you should obtain 79.4 mL of COmL of CO22 at 0 at 0°C and 760 mm Hg. How many °C and 760 mm Hg. How many milliliters of gas would you obtain at 27°C?milliliters of gas would you obtain at 27°C?

Combined Gas LawCombined Gas Law PV = constantPV = constant P P11VV11 = P = P22VV22

TT TT11 T T22

(for a given molar amount of gas)(for a given molar amount of gas)

Example:Example:Divers working from a North Sea oil drilling platform experience Divers working from a North Sea oil drilling platform experience pressures of 5.0x10pressures of 5.0x1011 atm at a depth of 5.0x10 atm at a depth of 5.0x1022m. If a balloon is m. If a balloon is inflated to a volume of 5.0L (the volume of a lung) at that depth at a inflated to a volume of 5.0L (the volume of a lung) at that depth at a water temperature of 4.0water temperature of 4.0°C, what would the volume of the balloon be °C, what would the volume of the balloon be on the surface (1.0 atm pressure) at a temperature of 11°C?on the surface (1.0 atm pressure) at a temperature of 11°C?

Avogadro’s LawAvogadro’s Law Relates Relates volumevolume and and molar amount. molar amount. One mole of any gas contains how many One mole of any gas contains how many

molecules?molecules? At STP, VAt STP, Vmm = =

Ideal Gas LawIdeal Gas Law

We can combine the empirical gas We can combine the empirical gas laws into one equation called the laws into one equation called the Ideal Gas LawIdeal Gas Law

There must be a proportionality There must be a proportionality constant that governs relationships constant that governs relationships of Empirical Gas Laws = Rof Empirical Gas Laws = R

R is the universal gas law constant.R is the universal gas law constant. R = 0.0821 L atm/mol KR = 0.0821 L atm/mol K

The Ideal Gas LawThe Ideal Gas Law

The ideal gas law is the quantitative The ideal gas law is the quantitative relationship between pressure, relationship between pressure, volume, moles volume, moles gasgas present, and present, and the the absolute temperature.absolute temperature.

Units are critical! Units are critical!

PV = nRT

Ideal Gas Law Examples and Ideal Gas Law Examples and ApplicationsApplications

A 50.0-L cylinder of nitrogen, NA 50.0-L cylinder of nitrogen, N22, has a , has a pressure of 17.1 atm at 23pressure of 17.1 atm at 23°C. What is the °C. What is the mass of nitrogen in the cylinder?mass of nitrogen in the cylinder?

What is the density of methane gas What is the density of methane gas (natural gas), CH(natural gas), CH44, at 125, at 125°C and 3.50 °C and 3.50 atm?atm?

Gas StoichiometryGas Stoichiometry

Example:Example:The following reaction can be used to The following reaction can be used to

produce pure oxygen gas:produce pure oxygen gas:

2 H2 H22OO2 2 (l) (l) 2 H 2 H22O (l) + OO (l) + O22 (g) (g)

Suppose I used 0.01 moles of HSuppose I used 0.01 moles of H22OO22. How . How many liters of oxygen gas will I get at many liters of oxygen gas will I get at 298K and 1 atm?298K and 1 atm?

Gas StoichiometryGas Stoichiometry

Example:Example:How many liters of chlorine gas, ClHow many liters of chlorine gas, Cl22, can be , can be obtained at 40obtained at 40°C and 787 mmHg from 9.41 °C and 787 mmHg from 9.41 grams of HCl according to the following grams of HCl according to the following reaction?reaction?

2 KMnO2 KMnO44 (s) + 16 HCl (l) (s) + 16 HCl (l)

8 H8 H22O (l) + 2 KCl (aq) + 2 MnClO (l) + 2 KCl (aq) + 2 MnCl22 (aq) + 5 Cl (aq) + 5 Cl22 (g)(g)

Dalton’s Law of Partial Dalton’s Law of Partial PressuresPressures

Dalton’s Law of Partial Dalton’s Law of Partial PressuresPressures

Partial pressure –

Dalton’s Law of Partial Pressures –

PPTT = P = PAA + P + PBB + P + PCC + … + …

Calculation of Partial Pressure Calculation of Partial Pressure of Gas in a Mixtureof Gas in a Mixture

A 100.0 mL sample of air exhaled from A 100.0 mL sample of air exhaled from the lungs is analyzed and found to the lungs is analyzed and found to contain 0.0830 g Ncontain 0.0830 g N22, 0.0194 g O, 0.0194 g O22, , 0.00640 g CO0.00640 g CO22, and 0.0041 g water , and 0.0041 g water vapor at 35vapor at 35°C. What is the partial °C. What is the partial pressure of each component and the pressure of each component and the total pressure of the sample?total pressure of the sample?