# Homework Help: Assumptions of Kinetic Theory: How big should a cubical element be?

1. Nov 29, 2015

### Lagraaaange

1. The problem statement, all variables and given/known data
Assuming uniform distribution. What must be the size of a cubical element of volume in the container so that the number of particles in each volume element may vary by 0.1% when the gas is as standard conditions. Probable deviation is given by N^(1/2) where N is the number of particles.

2. Relevant equations
Deviation: N^(1/2)

3. The attempt at a solution
I don't know what N is for standard conditions.

Ans. 3300Angstroms

2. Nov 29, 2015

### Staff: Mentor

There is no "N for standard conditions".

The particle number fluctuates by N1/2. At which value of N does this correspond to 0.1% of N?

Relating this to a volume is a step that comes afterwards.

3. Nov 29, 2015

### Lagraaaange

But one needs a volume
So we need 0.001N = N^1/2. Solving N = 1,000,000. But I don't see where to go from here without any more info?

4. Nov 30, 2015

### Staff: Mentor

Some problems need more than one step. Finding N is the first step, finding the volume is the second.
Good. Now you can find the volume that has (on average) 1 million particles in it. How many particles are in a mole? What is the volume of a mole at standard conditions?