10 drops of olive oil of radius 0.2 mm spread into a circular film of radius 14.6cm on surface of water Estimate the size of oil molecule?

Answer 1

Volume of one drop=4/3 x 22/7 x 0.2 x 0.2 x 0.2=0.03 cubic mm(approx)

Volume of 10 drops=10 x 0.03= 0.3 cubic mm__________(1)

Radius of the film=14.6 cm

Area of the film=22/7 x 14.6 x 14.6=670 square cm_____(2)

Now as the film is made of ten drops of olive oil, from eq.(1) and (2), we get,

Volume of film=0.3 cubic mm

Now if we assume that thickness(t) of the film=1 molecule of oil of diameter(d), we can obtain 'd' by formula, thickness(t)=volume of film/area of film(formula given in class 11 ncert)

t=0.3 cubic mm/670 square cm=5 x 10 raise to the power 9