the gas laws ap chemistry. e.g., gasoline vapors basics on gases composition of the atmosphere: ~78%...
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The Gas Laws
APChemistry
e.g., gasoline vapors
Basics on Gases
composition of the atmosphere: ~78% N2, ~21% O2
properties of gases: expand to fill containercompressibleform homogeneous mixtures
vapors: gases of substances that are normally liquids or solids
-- due to gas particles being…
1)
2)
far apart
in constant, random motion
F Equation for pressure:
AF
P A
N
m2
P N/m2 = Pa
1 atm… = 760 mm Hg= 760 torr= 101.325 kPa= 1.01325 bar
(1 bar = 105 Pa)
At a depth of 350 m (1150 ft), the hull pressure on a submarine
is 3.4 x 106 Pa (36 tons/ft2).
BAROMETER
airpressure
mercury (Hg)
vacuum
mercurybarometer
Close-up of an early mercury barometer,
showing how the mercury column is
supported by atmospheric pressure.
An aneroid barometer containsa small, pressure-sensitive
metal box that has beenevacuated of air. The box is
prevented from collapsing bybeing connected to a spring
that is also attached to the dialon the barometer. When
the air pressure on the wallsof the box changes, the box
“flexes,” which moves thespring and the dial.
OPEN END MANOMETER
CLOSED END MANOMETER
air pressure
Hg heightdifference
sealed end
confinedgas
SMALL + HEIGHT = BIG Pgas = HEIGHT
The Gas LawsBoyle’s law:
Robert Boyle(1627–1691)
PV = constant
(when T is constant)
P
V
V
1/P
Charles’s law:
Jacques Charles(1746–1823)
V/T = constant
(when P is constant)
T
V
**T in K
(0.00 K = –273.15oC)
Gay-Lussac’s law:
Joseph LouisGay-Lussac(1778–1850)
P/T = constant
(when V is constant)
T
P
(1876–1956)
i.e.,
Avogadro’s hypothesis:
Equal volumes of gas at thesame temperature andpressure have the samenumber of particles.
Amedeo Avogadro(1776–1856)
Avogadro’s law:
Volume of a gas isproportional to thenumber of moles of gas. n V
e.g., 22.4 L of ANY GAS at STP contains 6.02 x 1023 particles
Amedeo Avocado
Combined Gas law: merges Boyle’s, Charles’s, and Gay-Lussac’s laws into one equation.
2
22
1
11
T VP
T VP
**NOTE:
For all gas lawcalculations, use
the absolutetemperature (in K).
Ideal Gas law:
P V = n R TR = 8.314 L-kPa/mol-K = 0.08206 L-atm/mol-K
Conditions of standard temp. and pressure (STP): 0oC (273.15 K) 1 atm
Equations for gas density:
T R
P D
22
2
11
1
D T
P
D T
P
M = molar mass of gas
Other Equations and Constants
same gas; twosets of conditions
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