Define mole. Calculate the mass of one molecule of `H_(2)O`

Explanation

Mole, A mole is equal to `6.022 xx 10^(23)` particles. These particles may be atoms, molecules or ions. This number `6.022 xx 10^(23)` is also called Avogadro number.
For example, One mole of K atoms `= 6.022 xx 10^(23)` potassium atoms
One mole of electrons `=6.022 xx 10^(23)` electrons
Mass of one molecule of `H_(2)O` : Now, mass of one mole of water molecules
`=2 xx H + 1 xx O= 2 xx 1 + 16= 18g`
`6.022 xx 10^(23)` molecules of water has a mass= 18g
`therefore` 1 molecule of water has a mass `= (18)/(6.022 xx 10^(23))= 2.99 xx 10^(-23)g`
Thus, one molecule of water has a mas `=2.99 xx 10^(-23)g`