Question

The surface tension and vapour pressure of water at ${20}^{o}C$ is 7.28$\times {10}^{-2}$ N/m and $2.33\times {10}^3$ pa, respectively. What is the radius of the smallest spherical water droplet which can from without evaporating at ${20}^{o}C$ ?

• A. $5\times {10}^{-4}m$
• B. $6.25\times {10}^{-5}m$
• C. $9\times {10}^{-2}m$
• D. $3\times {10}^{-5}m$

Answer 1

Answer: (B)

$6.25\times {10}^{-5}m$

$\text{We know that}$

$P=\frac{2T}{r}$

$\Rightarrow r=\frac{2T}{P}$

$r=\frac{2\times 7.28\times {10}^{-2}{NM}^{-1}}{2.33\times {10}^3}$

$r=6.25\times {10}^{-5}$