Gases, liquids summary
Topics:
Properties of gases, ideal gas law, kinetic molecular model of
gases, non-ideality, intermolecular forces, properties of liquids.
Defnitions:
pressure, absolute zero, STP, molar volume, diffusion,
effusion, partial pressure, mean free path, root mean squared, inter/intra-
molecular, hydrogen bond, dispersion forces, vapor pressure, boiling point,
viscosity, surface tension, capillary action, adhesion/cohesion
Calculations:
Ideal gas law static problems; ideal gas law comparison/
dynamic problems; combine ideal gas law with equations for mass, density,
molecular weight or with stoichiometry
Applications:
assign appropriate intermolecular force to a molecule
Ranking:
relative gas speeds; non-ideality of gases, physical properties of
liquids, intermolecular force strength
Gases
•
For gases always work in Kelvin.
Temperature (K) = Temperature (˚C) + 273.15
•
STP = 1 atm, 0˚C
•
The
molar volume
of any ideal gas at STP = 22.414 L
•
Ideal Gas Law
:
PV = nRT
•
Boyle’s law (P,V), Charles’ law (P, T), and Avagadro’s law (V, n) can
all be derived from this
•
Static problems: we know three of the four variables, ±nd the fourth.
•
Dynamic problems: one or more variables are perturbed while the
others are held constant.
Static problem:
What do we know?
What is unknown?
Do you need to use an equation to find n from m, M, MW, density?
Do you need to include stoichiometry?
Rearrange the ideal gas law with the unknown on one side.
Solve, doing appropriate unit conversions, specially T into Kelvin.
1. If we completely combust 6 moles of glucose
(C
6
H
12
O
6
) in the presence of excess oxygen in a 22
liter container at 25˚C, what would be the total Fnal
pressure of the system in atmospheres?
2. If 56 g of liquid nitrogen evaporates at standard
temperature and pressure, what is the Fnal volume of
the gaseous nitrogen?
1
2
3