# Gases revision

not all equations for the kinetic theory of gases are here - look in your book -  that section is hard to summarise and explain.

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• Created on: 02-03-13 11:07
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### Page 1

Gases
In gas calculations, temperature MUST be in KELVINS.

Boyle's Law pV = k Constant T: water boils at fixed
p= k temp.
V
Pressure inversely proportional
to volume
Charles's Law V =k Constant p: Prince Charles!
T
Volume proportional to temp
Pressure Law P =k Only one left! Constant:…

### Page 2

Pressure Law

Explanation: pressure increased by temp. increase because average speed of molecule increased
due to heat= impacts on container walls harder and more often = increase temp.

For questions:

You will only ever need to use one law.

So, if you need to use Boyle's law, and the volume…

### Page 3

Avagadro used to find how many molecules are in a gas using 1g of H. We now used 12g 12-C
isotope because hydrogen gas was impure and the isotope of H, which made it impure, was hard to
remove.

1u: 1/12th mass of 12-C.
1u = 1.661x10-27 kg

pV = nRT

### Page 5

pV = nkT

Mass MS of substance: Mn

Mass of ideal gas: MS: M( pV /RT )

Density of ideal gas: MS/V = pM/RT

Boltzmann constant : k= R/NA

Each impact on container wall causes a force on it. The force of many impacts is the cause of the
pressure…

### Page 6

if temp of gas increased, molecules move faster on average. Distribution becomes flatter and

Root mean square speed:

Molecules are point molecules
Molecules don't have electrostatic forces - don't attract/ repel
Move in continual random motion
Elastic collisions ­ no overall loss of KE…