Question

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

Answer 1

Heat required for melting 1 mole (18 g) of ice $=330\times 18=5940J$
Energy of one photon $=hv$
$=6.6\times {10}^{-34}\times 5\times {10}^{13}=33\times {10}^{-21}J$
$\therefore$ Total number of photons required to produce 5940 J energy $=\frac{5940}{33\times {10}^{-21}}=18\times {10}^{22}$

therefore, $X=18$