Question:
The surface tension and vapour pressure of water at 20oC is 7.28 × 10-2 N/m and 2.33 × 103 Pa, respectively. What is the radius of the smallest spherical water droplet which can form without evaporating at 20oC?
Solution:
Surface tension of water, T = 7.28 × 10-2 N/m
Vapour pressure, P = 2.33 × 103 Pa
Radius of drop = r
2T/r is the excess pressure which is greater than the vapour pressure.
Vapour pressure = excess pressure in drop
Using the above relation, we can calculate r = 6.25 × 10-5 m
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