Question

if 1ml of water contain 20 drops, what is the number of molecules in a drop of water

Answer 1

Molarity of water is 55.49 M. So its 55.49 moles in 1 L of water. Now, 1 ml will have 55.49/1000 = 55.49 millimoles of water.

Now, 1 mmol = 6.022 x 10^20 molecules of water.

So 1 ml contains 55.49 x 6.022 x 10^20 molecules of water.

And therefore, 1 drop = 1/20 ml contains [55.49/20] x 6.022 x 10^20 molecules of water.

Final Answer : 16.708039 x 10 ^22 molecules of water.