Our cells continuously use oxygen and produce carbon dioxide Both gases move in and out of the lungs through the membranes of the alveoli the tiny air sacs at the ends of the airways in the lungs ID: 759775
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Slide1
8.8 Partial Pressure (Dalton’s Law)
Our cells continuously use oxygen and produce carbon dioxide. Both gases move in and out of the lungs through the membranes of the alveoli, the tiny air sacs at the ends of the airways in the lungs.
Learning Goal
Use Dalton’s law of partial pressures to calculate the total pressure of a mixture of gases.
Slide2Partial Pressure
The partial pressure of a gas is the pressure that each gas in a mixture would exert if it were by itself in the container.Core Chemistry Skill Calculating Partial Pressure
Slide3Dalton’s Law of Partial Pressures
Dalton’s law of partial pressures indicates thatpressure depends on the total number of gas particles, not on the types of particles.the total pressure exerted by gases in a mixture is the sum of the partial pressures of those gases. PT = P1 + P2 + P3 + ....
Slide4Total Pressure
For example, at STP, 1 mole of a pure gas in a volume of 22.4 L will exert the same pressure as 1 mole of a gas mixture in 22.4 L. Gas mixtures
1.0 mole N
2
0.4 mole O20.6 mole He1.0 mole
0.5 mole O20.3 mole He0.2 mole Ar1.0 mole
1.0 atm
1.0 atm
1.0 atm
Slide5Total Pressure
The air we breathe is a mixture of different gases.contains mostly N2 and O2, and contains small amounts of other gases.What we call the atmospheric pressure is actually the sum of the partial pressures of the gases in the air
Slide6Guide to Solving for Partial Pressure
Slide7Solving for Partial Pressure
A scuba tank contains O2 with a pressure of 0.450 atm and Heat 855 mmHg. What is the total pressure in mmHg in the tank (volume and temperature are constant)?STEP 1 Write the equation for the sum of the partial pressures. Ptotal = PO2 + PHeSTEP 2 Rearrange the equation to solve for the unknown pressure. Convert units to match. Ptotal = PO2 + PHe
Solving for Partial Pressure
A scuba tank contains O2 with a pressure of 0.450 atm and Heat 855 mmHg. What is the total pressure in mmHg in the tank (volume and temperature are constant)?STEP 3 Substitute known pressures and calculate the unknown partial pressure. Ptotal = PO2 + PHe Ptotal = 342 mmHg + 855 mmHg = 1.20 x 103 mmHg
Study Check
For a deep dive, a scuba diver uses a mixture
of helium and oxygen
with a pressure of 8.00 atm. If the oxygen has a
partial pressure
of 1280 mmHg, what is the partial pressure of the
helium
(volume
and temperature
are constant)?
A. 520 mmHg
B. 2040 mmHg
C. 4800 mmHg
Solution
For a deep dive, a scuba diver uses a mixture of helium and
oxygen with a pressure of 8.00 atm. If the oxygen has a partial pressure of 1280 mmHg, what is the partial pressure of the helium (volume and temperature are constant)?STEP 1 Write the equation for the sum of the partial pressures. Ptotal = PO2 + PheSTEP 2 Rearrange the equation to solve for the unknown pressure. Convert units to match.
PHe = Ptotal − PO2
×
Slide11Solution
For a deep dive, a scuba diver uses a mixture of helium and
oxygen with a pressure of 8.00 atm. If the oxygen has a
partial pressure of 1280 mmHg, what is the partial pressure of
the
helium (volume and temperature are constant)?
STEP 3
Substitute
known pressures and calculate
the unknown
partial pressure
.
P
He
= 6080 mmHg
–
1280 mmHg
=
4800 mmHg or 4.80
×
10
3
mmHg
The
answer is C, 4800 mm Hg.
Slide12Chemistry Link to
Health: Blood Gases
In the lungs, O
2
enters the blood, while CO
2
from the blood is released.
In the tissues, O
2
enters the cells, which releases CO
2
into
the blood.
Slide13Chemistry Link to Health: Blood Gases
In the body, O2 flows into the tissues because the partial pressure of O2 is higher in blood and lower in the tissues. CO2 flows out of the tissues because the partial pressure of CO2 is higher in the tissues and lower in blood.
Slide14Chemistry Link to Health:Partial Pressures in Blood
Partial Pressures in Blood and Tissue
Slide15Gas Exchange During Breathing
Slide16Concept Map, Gas Laws