15.1 Gases

15.1.1 : PV = nRT ... P=(pressure in atm) V=(volume in cm³) n=(number of atoms in mols) R=(82.05 cm³ atm K^-1 mol^-1 -- in data book) T=(temperature in K)

15.1.2 : The above equation can be rearranged as P₁V₁=P₂V₂ or V₁/T₁=V₂/T₂ if temp or pressure are assumed to be constant. Avogadro's law -- equal volumes of gas contain equal numbers of particles (at 273K, 1 atm -> 22.4 dm³ mol^-1 -- in data book)

15.1.3 : Dalton's law of partial pressures -> the partial pressure of a gas is the pressure the gas would exert if the gas were alone in its container. ie if there are Gases A, B and C filling a dm³, b dm³ and c dm³ respectively then the partial pressure of a = ^(a)/_(a+b+c) x total pressure.

15.1.4 : P_p = ^{(number of molecules in the gas)}/_{(total number of molecules)} x total pressure ... apply this relationship...

Nb -- Apparently, though it's never been in the syllabus, there have been questions on Van Der Wall's equation, which is an extension of PV=nRT for non-ideal gas situations...it is (P+an²/V²)(V-nb)=nRT Where a and b are constants for a given gas...which I assume will be given if necessary.

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