Number of molecules of water in 6 moles

I mol of anything is 6.02 * 10^23 (in this case molecules of water)
6 mols of water = x

1/6 = 6.02 * 10^23 / x Cross multiply
x = 6 * 6.02* 10^23
x = 3.612 * 10^24 molecules in 6 mols of water

Particle exchange energy though elastic collision , hope this .