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TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Chemistry > States of Matter - 15

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15.1 Gases

15.1.1

• pressure in atm
• volume in cm³
• number of atoms in mols
• 82.05 cm³ atm K</sup>-1</sup> mol^-1 -- in data book
• temperature in K

15.1.2

The above equation can be rearranged as:

or ,

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

where 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 for non-ideal gas situations. It is:

Where and are constants for a given gas, which I assume will be given if necessary.

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