Question

The latent heat of fusion of ice is $330J/g$. Calculate the number of photons of radiation of frequency $5\times {10}^{13}{s}^{-1}$ to cause the melting of $1mole$ of ice. Take $h=6.6\times {10}^{-34}J.se{c}^{-1}$. Express your answer as $x\times {10}^{22}$. What is the value of $x$?

Answer 1

Energy required to melt 1 mole of ice $=18\times 330J$

Energy given by '$n$' photons$=n\times hv$

$\therefore n\times h\times s\times {10}^{13}=18\times 330$

$n=\frac{18\times 330}{6.6\times {10}^{-34}\times 5\times {10}^{13}}$

$=\frac{5440}{33\times {10}^{-21}}=18\times {10}^{22}$

$\therefore x=18$