How many photons (wavelength = 620 nm) must be absorbed to melt a 2.0-kg block of ice at 0 °C into water at 0

(a) How many photons (wavelength = 620 nm) must be absorbed to melt a 2.0-kg block of ice at 0 °C into water at 0 °C? Assume all of the energy of the photon is used to melt the ice.
(b) On the average, how many H20 molecules does one photon convert from the ice phase to the water phase?

(Lf of water = 33.5 x 10^4 J

First calculate the energy of one photon (using E =hc/wavelength)
now calculate the energy used to convert 2 kg ice block into water, Q = mass * Lf
and equate,,
nE=Q , n is the no of photon
so n = Q/E = 2 *Lf/hc *wavelength

for no b
From above, n photon melt 2 kg,, so 1 photon melt 2/n kg = 2000/n gram = 2000/n * Na/18 molecules
Na = Avagadro's number