Calculate the approximate number of molecules in a drop of water with a mass of 0.10 g.
A.
3 × 1021 molecules
B.
2 × 1023 molecules
C.
6 × 1021 molecules
D.
4 × 1023 molecules

Option A. 3 × 10^21 molecules

Explanation:

From Avogadro's hypothesis, 1mole of any substance contains 6.02x10^23 molecules. This means that 1mole of H20 also contains 6.02x10^23 molecules.

1mole of H2O = (2x1) + 16 = 2 + 16 = 18g

If 1mole(i.e 18g) of H2O contains 6.02x10^23 molecules,

Therefore 0.1g of H2O will contain = (0.1 x 6.02x10^23) /18 = 3 x 10^21 molecules

catya your not at all which answer i've seen you do this on another question!

it is b that is the answer.