Question

If 1 ml of water contains 20 drops ,then number of molecules in drop of water is

Answer 1

Answer:

Considering that 1 ml of water has a mass of 1 gram, calculate moles of 1 drop.

20 drops = 1ml

then 1 drop = 1x1/20

=0.05ml

therefore if 1ml = 1g

then 0.05ml= 0.05g( mass of 1 drop of water)

molar mass of H2O= 18

Hence its moles= 0.05/18 = 2.7778x10^-3

Avagadros constant: 1 mole = 6.023x10^23 molecules

if 1 mole = 6.023x10^23molecules

then 2.7778x10^-3= 6.023x10^23 x 2.7778x10^-3 molecules

=1.6731 x 10^21 molecules (in a drop of water)