Gasses

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Skills tested by this Quiz

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:

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

Pi Vi = k (k is a constant)
Pi Vi = Pf Vf

Charles Law

T = 273.15 + tC

     Vi     Vf
     --  =  --  = k
     Ti     Tf

     Pi     Pf
     --  =  --  = k
     Ti     Tf

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 Ptotal is the total pressure of a gas mixture, Pa , Pb , Pc , ... are partial pressures of gas A, B, C, ..., then

Ptotal = Pa + Pb + Pc + ... If ntotal is the total number of mole, and na , nb , nc , ... are number of moles of gas A, B, C, ..., then ntotal = na + nb + nc ...
    nt R T  = P V 
= (na + nb + nc + ...) R T
= Pa + Pb + Pc
+ ...

Mole fraction

The mole fraction of a gas A, xa in a system containing ntotal mole of gas is xa = na / ntotal

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 non-ideal behavior of gas, and the van der Waals equation

(P + n2a / V2) (V - n b) = n R T, has been introduced to deal with non-ideal behavior of gases, in Ideal gas law. For practical application in chemical manufacturing process and in chemical reactions, the non-ideality 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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