An ideal gas is under standard conditions. Find the diameter of the sphere within whose volume the relative fluctuation of the number of molecules is equal to η = 1.0.10-3. What is the average number of molecules inside such a sphere?
In a sphere of diameter d there are
where n0 = Loschmidt'* number = No. of molecules per unit volume (1 cc) under NTP.
The relative fluctuation in this umber is
The average number of molecules in this sphere is 1/η2 = 106
