A drop of olive oil of radius 0.25 mm spreads into a circular film of radius 5 cm on the water surface. Estimate the molecular size of the olive oil

Explanation

Area of the film, `A=pir^2cm^2`
`=25 pi cm^2` [`because` Radius of the film, r=5cm]
Volume of the drop, V=`4/3pi "(Radius of oil drop)"^3`
`=4/3xxpixx(0.25 mm)^3`
`=4/3xxpixx(2.5xx10^(-1))^3 mm^3`
`=4/3xxpixx15.6xx10^(-3)mm^3`
`=4/3xxpixx15.6xx10^(-6) cm^3`
Molecular size = Thickness of the film
`=V/A`
`=(4pixx15.6xx10^(-6))/(3xx25pi)`
`=0.83xx10^(-6)` cm
`=8.3xx10^(-9)` m