Question

Calculate the vapour pressure that can help the formation of a spherical droplet of water of radius $25 \times 10^{-5}\text{ m}$ at $22^\circ\text{C}$. Given: The surface tension of water at the given temperature is $28 \times 10^{-2}\text{ N m}^{-1}$.

• A. $8.81 \times 10^{3}\text{ Pa}$
• B. $2.33 \times 10^{3}\text{ Pa}$
• C. $6.64 \times 10^{4}\text{ Pa}$
• D. $1.01 \times 10^{5}\text{ Pa}$

Hint:

Be very careful when reading the question context. A water droplet has only $1$ free surface layer, so $\Delta P = \frac{2T}{r}$. If it were a soap bubble suspended in air, it would have $2$ free surfaces, changing the formula to $\Delta P = \frac{4T}{r}$.

Answer 1

The Correct Option is B