The surface tension and vapor pressure of water at `20^(@)`C is `7.28 xx 10^(-2) N m^(-1)` and `2.33 xx 10^(3)` Pa respectively. The radius of the smallest spherical water droplet which can form without evaporating at `25^(@)`C is

Options

A. `1.25 xx10^5m`
B. `6.25 xx10^5m`
C. `4.3 xx10^8m`
D. `3.4 xx10^3m`

Answer

B

Explanation

Here, `S = 7.28 xx 10^(-2)Nm^(-1),P = 2.33xx10^3` Pa
The drop will evaporate if the water pressure is greater than the vapour pressure P.
As `P=(2S)/R` where R is the radius of drop
`:.R = (2S)/P= (2xx7.28xx10^(-2))/(2.33xx10^3) = 6.25 xx10^5`
The radius of the smallest spherical water droplet which can form without evaporating.