Gasses
Skills tested by this Quiz
 Identify the theory applicable to each problem, and calculate
the desirable quantity from a given set of conditions.
Properties of Gases
Quiz tests your comprehension and abbility to apply the following topics to
solve problems.
Gases  the gaseous state of matter
Gas laws  the ABCD gas laws
Ideal gas law  a summary of gas laws
Gas kinetics  motion of gas molecules
Gas & stiochiometry  stoichiometry problems involving gases
A brief review is again here, but it is your responsibility to
identify the theory applicable to each problem, and calculate
the desirable quantity from a given set of conditions.
There are always more than one way to solve a problem, and a logical
approach is a useful skill in itself. It is the process of problem
solving, not the result, that is useful to you.
Common gas properties
Gas is a state of matter. In this state, all substances behave alike.
The properties of gaseous state are:

Amount of gas in moles, n, number of molecules, mass, and volume.

The pressure, P, exerted to the walls of the container by gas molecules
or by the wall to contain the gas to a fixed volume V.

The temperature, T, which is a measure of the kinetic energy of
the molecules.

The volume, V, occupied by a gas at temperature T, under the
pressure P.

The average kinetic energy of a gas, and the root mean square speed of
gas molecules.
These properties are often expressed in various units, and ability to
convert units from one to another is always required.
Gas laws  some key equations
You are expected to have mastered the
ABCD laws of gases.
You should use the proper units for pressure, P, volume V,
and temperature T. Letters i and f following these
quantities refer to the initial and final states respectively.
A summary of key equations is given below, but you should be able to
derive one from each other, and understand the system from which these
formulas apply.
Boyle's Law
P_{i} V_{i} = k (k is a constant)
P_{i} V_{i} = P_{f} V_{f}
Charles Law
T = 273.15 + t^{C}
V_{i} V_{f}
 =  = k
T_{i} T_{f}
P_{i} P_{f}
 =  = k
T_{i} T_{f}
The ideal gas law
P V = n R T
where
R = (1 atm 22.4 L)/(1 mol 273.15 K)
= 0.082058 L atm / (mol K)
= 8.3145 J / (mol K)
Avogadros law and gas density
n = P V / R T
n M
P M =  R T  where M is the molecular weight of the gas
V
P V = n R T  Ideal gas equation
P = d R T / M  where d is the density of the gas
d = P M / R T  density of gas is given by this equation
M = d R T / P  hence, the Molecular Weight of a gas is given by this.
Dalton's law of partial pressures
If P_{total} is the total pressure of a gas mixture,
P_{a} , P_{b} , P_{c} , ... are
partial pressures of gas A, B, C, ..., then
P_{total} = P_{a} + P_{b} + P_{c} + ...
If n_{total} is the total number of mole, and
n_{a} , n_{b} , n_{c} , ... are
number of moles of gas A, B, C, ..., then
n_{total} = n_{a} + n_{b} + n_{c} ...
n_{t} R T = P V
= (n_{a} + n_{b} + n_{c} + ...) R T
= P_{a} + P_{b} + P_{c} + ...
Mole fraction
The mole fraction of a gas A, x_{a} in a system
containing n_{total} mole of gas is
x_{a} = n_{a} / n_{total}
Non ideal behavior of gas
The ideal gas law has a limited precision for predicting the properties
of gases. The imprecision is known as the nonideal behavior of gas, and the
van der Waals equation
(P + n^{2}a / V^{2}) (V  n b) = n R T,
has been introduced to deal with nonideal behavior of gases, in
Ideal gas law.
For practical application in chemical manufacturing process and in chemical
reactions, the nonideality has to be taken into account.
For these applications, other methods of correction to the ideal gas law
are also used.
Practice Questions
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