gases part 1. elements that exist as gases at 25 0 c and 1 atmosphere
TRANSCRIPT
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Gases
Part 1
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Elements that exist as gases at 250C and 1 atmosphere
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• Gases assume the volume and shape of their containers.
• Gases are the most compressible state of matter.
• Gases will mix evenly and completely when confined to the same container.
• Gases have much lower densities than liquids and solids.
Physical Characteristics of Gases
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Units of Pressure
1 pascal (Pa) = 1 N/m2
1 atm = 760 mm Hg = 760 torr
= 101,325 Pa = 14.7 psi = 29.92 in. Hg
Barometer
Pressure = ForceArea
(force = mass x acceleration)
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Sea level 1 atm
4 miles 0.5 atm
10 miles 0.2 atm
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Boyle’s LawBoyle’s LawP P αα 1/V 1/VThis means Pressure and This means Pressure and
Volume are INVERSELY Volume are INVERSELY PROPORTIONAL if moles PROPORTIONAL if moles and temperature are and temperature are constant (do not change). constant (do not change). For example, P goes up as For example, P goes up as V goes down.V goes down.
PP11VV11 = P = P22 V V22
Robert Boyle Robert Boyle (1627-1691). (1627-1691). Son of Earl of Son of Earl of Cork, Ireland.Cork, Ireland.
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Charles’s Charles’s LawLaw
If n and P are constant, If n and P are constant,
then V then V αα T TV and T are directly V and T are directly
proportional.proportional.VV11 V V22
==
TT11 T T22
• If temperature goes up, the If temperature goes up, the
volume goes up!volume goes up!
Jacques Charles Jacques Charles (1746-1823)(1746-1823)
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Gay-Lussac’s LawGay-Lussac’s LawIf n and V are If n and V are
constant, constant, then P then P αα T T
P and T are directly P and T are directly proportional.proportional.
PP11 P P22
==
TT11 T T22
If temperature goes up, the If temperature goes up, the
pressure goes up!pressure goes up!
Joseph Louis Gay-Joseph Louis Gay-Lussac (1778-1850)Lussac (1778-1850)
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Combined Gas Law• The good news is that you don’t have to
remember all three gas laws! Since they are all related to each other, we can combine them into a single equation. BE SURE YOU KNOW THIS EQUATION!
P1 V1 P2 V2
=
T1 T2
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STP in chemistry stands for Standard Temperature and
PressureStandard Pressure =
1 atm (or an equivalent)
Standard Temperature = 0 deg
C (273 K)
STP allows us to compare amounts of
gases between different pressures and temperatures
STP allows us to compare amounts of
gases between different pressures and temperatures
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Avogadro’s Law
V number of moles (n)
V = constant x n
V1/n1 = V2/n2
Constant temperatureConstant pressure
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Ideal Gas Equation
Charles’ law: V T(at constant n and P)
Avogadro’s law: V n(at constant P and T)
Boyle’s law: V (at constant n and T)1P
V nT
P
V = constant x = RnT
P
nT
PR is the gas constant
PV = nRT
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The conditions 0 0C and 1 atm are called standard temperature and pressure (STP).
PV = nRT
R = PVnT
=(1 atm)(22.414L)
(1 mol)(273.15 K)
R = 0.082057 L • atm / (mol • K)Experiments show that at STP, 1 mole of an ideal gas occupies 22.414 L.
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Density (d) Calculations
d = mV =
PMRT
m is the mass of the gas in g
M is the molar mass of the gas
Molar Mass (M ) of a Gaseous Substance
dRTP
M = d is the density of the gas in g/L
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A 2.10-L vessel contains 4.65 g of a gas at 1.00 atm and 27.00C. What is the molar mass of the gas?
dRTP
M =