Transcript CHEM 5013 Applied Chemical Principles

CHEM 5013
Applied Chemical Principles
Chapter Five
Professor Bensley
Alfred State College
Chapter Objectives
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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.
Properties of Gases
1.
2.
3.
4.
5.
Pressure
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Pressure:
Gas Pressure
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Pressure is the
result of molecular
collisions between
gas molecules and
container walls.
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A barometer is
used to measure
pressure.
Units of Pressure and STP
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1
1
1
1
torr = 1 mm Hg
atm = 760 torr = 760 mm Hg (exactly)
atm = 101,325 Pa (exactly)
atm = 14.7 psi
At sea level, atmospheric pressure is?
Standard Temperature and Pressure
Conditions (STP):
Empirical Gas Laws
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Gases behave simply under “moderate”
conditions with respect to four things:
1)
2)
3)
4)
Boyle’s Law
PV = constant
For a given amount of gas at a constant temp.
P 1 V1 = P 2 V2
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.
Examples
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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?
Combined Gas Law
PV = constant
T
(for a given molar amount of gas)
P1V1 = P2V2
T1
T2
Example:
Divers working from a North Sea oil drilling platform
experience pressures of 5.0x101 atm 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?
Avogadro’s Law
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Relates volume and molar amount.
One mole of any gas contains how many
molecules?
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At STP, Vm =
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Ideal Gas Law
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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.
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R = 0.0821 L atm/mol K
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The Ideal Gas Law
PV = nRT
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The ideal gas law is the quantitative
relationship between pressure, volume,
moles gas present, and the absolute
temperature.
Units are critical!
Ideal Gas Law Examples and
Applications
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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)
Dalton’s Law of Partial Pressures
Dalton’s Law of Partial Pressures
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Partial pressure –
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Dalton’s Law of Partial Pressures –
PT = P A + P B + P C + …
Calculation of Partial Pressure of
Gas in a Mixture
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?