If 1 mL of water contains 20 drops then number of molecules in a drop of water is

(i) ∵ For water density = 1 g/ml∴ 1000 mL = 1000 g(ii) ∵ Number of moles of water in 1000 g (n) =wm (molar mass) n=100018=55.56moles∴Number of moles in I mL of water (n) = 55.61000                                                      (n) = 0.0556moles(iii) ∵1 mL of H2O contain 20 drops∴   Number of moles of H2O in one drop =0.055620                                                         (n)Pet drop = 0.0027(iv) ∵n=NNA=N6.023×1023N=n×NA=0.002×6.023×1023N=0.0162×1023=0.62×1021