Question

How many molecules are in a mole of H2O

Answer 1

1023 molecules or atoms depending on substance

Answer 2

According to this relationship, every mole has 6.022⋅1023 atoms (or molecules, depending on the substance). Since water is a molecule, 1 mole of water will always have 6.022⋅1023 molecules of water.

Hope this help! :D