Question

Why only 18.01 grams of water has 6.022×10^23
why not in any other mass

Answer 1

A mole (mol) is a number of things equal to the number of atoms in exactly 12 g of carbon-12. Experimental measurements have determined that this number is very large:

1 mol = 6.02214179 × 10²³things

Understand that a mole means a number of things, just like a dozen means a certain number of things—twelve, in the case of a dozen. But a mole is a much larger number of things. These things can be atoms, or molecules, or eggs; however, in chemistry, we usually use the mole to refer to the amounts of atoms or molecules.

So 18.01g of water contain 1 mole
No.of moles=given mass/molar mass
=18.01/18.01
=1
​​​Molar mass of water =18g
From one mole contain 6.022*10^23 molecules (As water is a molecule H2O)
So it does not contain any other mass other than this