To solve this problem, we can use the following formula:
q = nΔH
where q is the energy change, n is the number of moles, and ΔH is the enthalpy of fusion.
First, we need to calculate the number of moles of water:
n = m/M
where m is the mass of water and M is the molar mass of water.
m = 55.8 g
M = 18.015 g/mol
n = 55.8 g / 18.015 g/mol = 3.099 mol
Now, we can calculate the energy change:
q = nΔH
q = (3.099 mol) x (6.01 kJ/mol) = 18.6 kJ
Therefore, the energy change when 55.8 g of H2O melts at 0°C is 18.6 kJ.