Question

the heat of fusion or pure silicon is 43.4kj/mol. how much energy would be needed to melt a 5.24g sample of silicon as its melting point is 1693k

Answer 1

1) Convert the 5.24 grams to moles of Si
2) Multiply the number of moles from 1) by 43.4 kJ/mol
That will give you the amount of energy needed to melt the sample.
The 1693 K is just the temperature at which the phase change occurs but is not needed
to solve for the amount of energy needed.