Question: how many water molecules are there in one drop of water?
Answer: Using Avogadro's Number So, next, we calculate how many molecules there are in a drop of water, which we determined: molecules in a water drop = (6.022 x 102^3 molecules/mole) x 0.002275 moles. molecules in a water drop = 1.67 x 10^21 molecules of water.