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# CHEM 5013 Applied Chemical Principles - PowerPoint PPT Presentation

CHEM 5013 Applied Chemical Principles. Chapter Five Professor Bensley Alfred State College. Chapter Objectives. Describe the physical properties of gases. Use the ideal gas law for calculating changes in the conditions of gases .

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### CHEM 5013Applied Chemical Principles

Chapter Five

Professor Bensley

Alfred State College

• Describe the physical properties of gases.

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

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

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

• Pressure:

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

• A barometer is used to measure pressure.

Units of Pressure and STP

• 1 torr = 1 mm Hg

• 1 atm = 760 torr= 760 mm Hg (exactly)

• 1 atm = 101,325 Pa (exactly)

• 1 atm = 14.7 psi

• At sea level, atmospheric pressure is?

• Standard Temperature and Pressure Conditions (STP):

• Gases behave simply under “moderate” conditions with respect to four things:

PV = constant P1V1 = P2V2

For a given amount of gas at a constant temp.

Charles’s Law

V/T = constant V1 / T1=V2 / T2

For a given amount of gas at a given pressure

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

• A volume of oxygen gas occupies 38.7 mL at 751 mm Hg at 21°C. What is the volume if the pressure changes to 359 mm Hg and temp. remains constant?

• You prepared carbon dioxide by adding HCl(aq) to marble chips (CaCO3). According to your calculations, you should obtain 79.4 mL of CO2 at 0°C and 760 mm Hg. How many milliliters of gas would you obtain at 27°C?

PV = constant P1V1 = P2V2

TT1 T2

(for a given molar amount of gas)

Example:

Divers working from a North Sea oil drilling platform experience pressures of 5.0x101atm at a depth of 5.0x102m. If a balloon is inflated to a volume of 5.0L (the volume of a lung) at that depth at a water temperature of 4.0°C, what would the volume of the balloon be on the surface (1.0 atm pressure) at a temperature of 11°C?

• Relates volume and molar amount.

• One mole of any gas contains how many molecules?

• At STP, Vm =

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

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

• R is the universal gas law constant.

• R = 0.0821 L atm/mol K

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

• Units are critical!

• A 50.0-L cylinder of nitrogen, N2, has a pressure of 17.1 atm at 23°C. What is the mass of nitrogen in the cylinder?

• What is the density of methane gas (natural gas), CH4, at 125°C and 3.50 atm?

Gas Stoichiometry

Example:

The following reaction can be used to produce pure oxygen gas:

2 H2O2 (l)  2 H2O (l) + O2 (g)

Suppose I used 0.01 moles of H2O2. How many liters of oxygen gas will I get at 298K and 1 atm?

Gas Stoichiometry

Example:

How many liters of chlorine gas, Cl2, can be obtained at 40°C and 787 mmHg from 9.41 grams of HCl according to the following reaction?

2 KMnO4 (s) + 16 HCl (l) 

8 H2O (l) + 2 KCl (aq) + 2 MnCl2 (aq) + 5 Cl2 (g)

• Partial pressure –

• Dalton’s Law of Partial Pressures –

PT = PA + PB + PC + …

A 100.0 mL sample of air exhaled from the lungs is analyzed and found to contain 0.0830 g N2, 0.0194 g O2, 0.00640 g CO2, and 0.0041 g water vapor at 35°C. What is the partial pressure of each component and the total pressure of the sample?