Answer: number of molecules in one drop of water.

Solution:

1 mL of water contains:

Density of water = 1 g/mL

Mass of water =

Number of moles in 1 mL=

According to question in 1 mL there are 20 drops, then number of mole in one drop will be:

Number of molecules in the drop of water:

Then in 0.0027 moles of water :

number of molecules in one drop of water.