Q3 / 90 · KVPY 2011 (SB/SX) · Chemistry
Emulsification of $10 \mathrm{ml}$ of oil in water produces $2.4 \times 10^{18}$ droplets. If the surface tension at the oil-water interface is $0.03 \mathrm{Jm}^{-2}$ and the area of each droplet is $12.5 \times 10^{-16} \mathrm{~m}^{2}$, the energy spent in the formation of oil droplets is-
- Correct answerA$90 \mathrm{~J}$
- B$30 \mathrm{~J}$
- C$900 \mathrm{~J}$
- D$10 \mathrm{~J}$
Solution
Total droplets $=2.4 \times 10^{18}$
total area $=$ total droplets $\times$ area of one drop
$=2.4 \times 10^{18} \times 12.5 \times 10^{-16}$
$=12.5 \times 2.4 \times 10^{2} \mathrm{~m}^{2}$
Energy consumption
$\begin{array}{l}
=0.03 \times 12.5 \times 2.4 \times 10^{2} \\
=90 \text { Joule }
\end{array}$
Hence, the correct answer is option: 'A'.