Question

Calculate the number of molecules in a drop of water.Given that 20 drops of water weigh 1.2 gram

Answer 1

Mass of 20 drops of water = 1.2g

Mass of 1 drop of water = 1.2/20 = 0.06g

Molar mass of water = 18g

Moles of water = given mass / molar mass

= 0.06/18

= 0.0033

Therefore, no. Of water molecules,

= 0.0033 X 6.022 X 10^23

= 0.0198 X 10^23

= 1.98 X 10^23

Answer 2

Explanation:

Molecular mass of H

O

=18g=1mole

18g of water contains 6.022×10

23

molecules.

∴0.18g of water contains, =

18

0.18×6.023×10

23

=0.06023×10

23

=6.023×10

23

molecules.