1.7 Kinetic theory Flashcards
Define mole
The amount of a substance that contains as many molecules as exactly 12g of carbon-12
Define the Avogadro constant
The number of molecules in a mole. It is given by the value 6.022 x 10^23, and has units mol^-1
Define molar mass
The molar mass of a substance is the mass per mol
Define unified atomic mass unit
The unified atomic mass unit, u, is 1/12 of the mass of an isolated carbon-12 atom in its nuclear and atomic ground state
Define an ideal gas
An ideal gas is one which strictly follows the equation pV = nRT
What is the kinetic theory of gases?
A gas consists of point molecules moving about in random motion
What are the 6 assumptions required for an ideal gas?
- Molecules are points
- Molecules do not attract each other, their motion is independent of each other
- Molecules move in constant, random motion
- All collisions between molecules and their container are elastic
- The time taken for a collision is much shorter than the time between collisions
- Any sample of an ideal gas contains a very large number of molecules
Define Boyle’s law
Pressure is inversely proportional to volume
Define Charles’ law
Volume is proportional to temperature
Define Amonton’s law
The pressure of a given mass of a gas varies directly with the absolute temperature of the gas when the volume is kept constant
Define mean square speed
The mean value of the squares of the molecular speeds. The square root of this is known as the root mean square speed, or rms speed
What are the two forms of the ideal gas equation?
- pV = nRT, where n is the number of moles
- pV = NkT, where N is the number of molecules
What equation links pressure and molecular motion?
pV = (1/3)Nm(mean square speed)
Define mean kinetic energy per molecule
Mean KE = (3/2)kT
Define molar heat capacity
At constant volume, the molar heat capacity is the heat required to raise the temperature of 1 mol of the gas by 1K without changing the volume
