Gases Part 1. Elements that exist as gases at 25 0 C and 1 atmosphere. Physical Characteristics of Gases. 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.
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Elements that exist as gases at 250C and 1 atmosphere
Physical Characteristics of Gases
(force = mass x acceleration)
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
P α 1/V
This means Pressure and Volume are INVERSELY PROPORTIONAL if moles and temperature are constant (do not change). For example, P goes up as V goes down.
P1V1 = P2 V2
Robert Boyle (1627-1691). Son of Earl of Cork, Ireland.
If n and P are constant, then V α T
V and T are directly proportional.
Jacques Charles (1746-1823)
If n and V are constant, then P α T
P and T are directly proportional.
If temperature goes up, the pressure goes up!
Joseph Louis Gay-Lussac (1778-1850)
P1 V1 P2 V2
STP in chemistry stands for Standard Temperature and Pressure
Standard 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
Va number of moles (n)
V = constant x n
V1/n1 = V2/n2
Boyle’s law: V a (at constant n and T)
V = constant x = R
Charles’ law: VaT(at constant n and P)
Avogadro’s law: V a n(at constant P and T)
R is the gas constant
PV = nRT
(1 mol)(273.15 K)
The conditions 0 0C and 1 atm are called standard temperature and pressure (STP).
PV = nRT
R = 0.082057 L • atm / (mol • K)
Experiments show that at STP, 1 mole of an ideal gas occupies 22.414 L.
Density (d) Calculations
m is the mass of the gas in g
M is the molar mass of the gas
Molar Mass (M ) of a Gaseous Substance
d is the density of the gas in g/L
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?