question_answer 51)

                  The sufrace tension and vapour pressure of water at \[{{20}^{o}}C\] is \[7.28\times {{10}^{-2}}\,N\,{{m}^{-1}}\] and \[2.33\times {{10}^{3}}\,Pa\], respectively. What is the radius of the smallest spherical water droplet which can form without evaporating at \[{{20}^{o}}C\]?                

Answer:

                  Using \[p=\frac{2T}{r}\] (excess pressure in a drop)                 \[r=\frac{2T}{p}=\,\frac{2\times \,7.28\,\times \,{{10}^{-2}}}{2.33\,\times \,{{10}^{3}}}\]                 \[=6.25\times {{10}^{-5}}\,m\]