unit 5 Flashcards
gas properties
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low density
changes dramatically with a change in pressure/temp
volume, pressure, temperature are interrelated
pressure
force exerted per unit area as gas molecules strike the surfaces around them
unit equalities
- mm Hg = 760. torr = 1 atm = 101.3 kPa = 14.7 psi
mm Hg (millimeters of mercury)/torr
atmospheric pressure that can support a column of mercury that is 760. mm high in a barometer
atmospheres (atm)
avg. pressure at sea level
pascal (Pa)
SI unit of pressure
also expressed as kPa
psi (lbs per square inch)
measure of force per unit area
boyle’s law
p1v1=p2v2
volume increases = pressure decreases
Charles law
v1/t1 = v2/t2
volume increases = temperature increases
always positive
avogadro’s law
v1/n1 = v2/n2
volume increases = moles increase
Gay-Lussac’s law
p1/t1 = p2/t2
pressure increases = temperature increases
combined gas law
p1v1/t1 = p2v2/t2
ideal gas law
PV = nRT
P: pressure in atm
V: volume in L
n: moles in mol
R: ideal gas constant (0.08206 when Latm/molK)
T: temperature in K
molar volume
volume occupied by 1 mol of a substance
standard temperature and pressure (STP)
for gases, molar volume is usually STP (1.00 atm)
density =
molar mass / molar volume
molar mass increases = density increases
1 mol of an ideal gas occupies:
22.4 L at STP
density of a gas equation
d = PM / RT
d: density in g/L
P: pressure in atm
M: molar mass in g/mol
R: ideal gas constant (0.08206 when Latm/molK)
T: temperature in K
to find molar mass of a gas:
measure mass and volume under known conditions of T and P
use ideal gas law to determine amount of gas in mol
divide mass by moles to get molar mass
partial pressure
pressure due to an individual component of a gas
Pn = Nn RT/V
Dalton’s Law of Partial Pressures
sum of partial pressures in a gas mixture = total pressure
P(total) = P(a) + P(b) + P(c)
mole fraction (X(a))
X(a) = N(a)/N(total)
or
P(a) = X(a)P(total)
gas mole fraction
percent by volume / 100
Vapor pressure
gas mixture with partial pressures
temp increases = Vapor pressure increases
