Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in...
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Transcript of Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in...
![Page 1: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/1.jpg)
The Nature of Gases – Part 2
Gas Pressure
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Objectives
When you complete this presentation, you will be able to: describe gas pressure in terms of the
motion of gas particles. describe the invention of the barometer. describe the derivation of the units of
pressure. convert between the units of pressure.
![Page 3: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/3.jpg)
Introduction
Gas pressure is the result of the force of gas molecules exerted on a surface.
The force of a single molecule of gas in insignificant, but the force of trillions of molecules becomes measurable.
A vacuum is a volume where there are no gas molecules bouncing off a surface.
Atmospheric pressure results from the collision of air molecules with objects.
![Page 4: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/4.jpg)
Measuring Pressure
We measure the pressure of a gas by using an instrument called a barometer.
The barometer was invented in 1643 by the Italian physicist Evangelista Torricelli.
He made a barometer from a tube of glass (sealed at one end) and a trough of mercury.
![Page 5: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/5.jpg)
Measuring Pressure
We measure the pressure of a gas by using an instrument called a barometer.
The barometer was invented in 1643 by the Italian physicist Evangelista Torricelli.
He made a barometer from a tube of glass (sealed at one end) and a trough of mercury.
![Page 6: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/6.jpg)
Measuring Pressure
We measure the pressure of a gas by using an instrument called a barometer.
The barometer was invented in 1643 by the Italian physicist Evangelista Torricelli.
He made a barometer from a tube of glass (sealed at one end) and a trough of mercury.
The air pressure on the Hg held the column up.
![Page 7: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/7.jpg)
Pressure Units
The air pressure in a barometer is measured by measuring the height of the mercury column.
Under standard conditions, a column of mercury will be 760 mm in height.
So, we say that 1 atmosphere of pressure (1 atm) is equal to 760 mm Hg.
![Page 8: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/8.jpg)
Pressure Units
Another unit for pressure uses SI units for force (newtons, N) per area (m2) which is called a Pascal, (Pa).
Under standard conditions, 1 atm of pressure is equal to 101,300 Pa = 101.3 kPa.
![Page 9: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/9.jpg)
Pressure Units
Our conversions are:
1.000 atm = 760.0 mm Hg = 101.3 kPa
![Page 10: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/10.jpg)
Let’s do some examples
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Example 1
A container of oxygen gas has a pressure of 0.450 atm. Find the pressure in mm Hg and kPa.
Conversions:1.000 atm = 760.0 mm Hg = 101.3 kPa
Solution:0.450 atm1 = =
760.0 mm Hg1.000 atm 342 mm
Hg
0.450 atm1 = =
101.3 kPa1.000 atm 45.6 kPa
![Page 12: Gas Pressure. When you complete this presentation, you will be able to: describe gas pressure in terms of the motion of gas particles. describe.](https://reader035.fdocuments.in/reader035/viewer/2022062515/56649cec5503460f949b8ae9/html5/thumbnails/12.jpg)
Example 2
A container of nitrogen gas has a pressure of 855 mm Hg. Find the pressure in atm and kPa.
Conversions:1.000 atm = 760.0 mm Hg = 101.3 kPa
Solution:855 mm Hg1 = =
1.000 atm760.0 mm
Hg
1.13 atm
855 mm Hg1 = =
101.3 kPa760.0 mm
Hg
114 kPa
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Example 3
A container of hydrogen gas has a pressure of 97.3 kPa. Find the pressure in atm and mm Hg.
Conversions:1.000 atm = 760.0 mm Hg = 101.3 kPa
Solution:97.3 kPa1 = =
1.000 atm101.3 kPa
0.961 atm
97.3 kPa1 = =
760.0 mm Hg101.3 kPa
730 mm Hg
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Practice Problems
Fill in the blanks for each of the following pressures
Conversions:1.000 atm = 760.0 mm Hg = 101.3 kPa
atm mm Hg kPa
3.00
950
76.0
0.742
600
258
2,280 304
1.25 127
0.750 570
564 75.2
0.789 80.0
2.55 1,940
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Summary
Gas pressure is the result of the force of gas molecules exerted on a surface.
Atmospheric pressure results from the collision of air molecules with objects.
We measure the pressure of a gas by using an instrument called a barometer invented in 1643 by the Italian physicist Evangelista Torricelli.
Our conversions are:1.000 atm = 760.0 mmHg = 101.3 kPa