the mass of ice taken = 10 g
the mass of water = 250 g
initial temperature of water = 20 C
the final temperature of water = 16. 8 C
specific heat of water = 4.18 J/g*K
the heat absorbed by ice to melt = heat loss by water
heat loss by water = mass X specific heat of water X change in temperature
heat loss by water = 250 X 4.18 X (20-16.8) = 3344 Joules
heat gained by ice = 3344 J
heat gained by ice = enthalpy of fusion X moles of ice
moles of ice = mass / molar mass = 10 / 18 = 0.56 moles
enthalpy of fusion = 3344 / 0.56 = 5971.43 J / mole