Question

Help me please!

The molar heat of fusion of platinum (Pt) is 4.700 kcal/mol. How much heat must be added to 85.5 g of solid platinum at its melting point to completely melt it?

Answer 1

The molar mass of platinum is 195.1 g/mol. So 85.5g*(mol/195.1 g)= 0.438 mol Pt. If 1 mol of Pt requires 4.700 kcal of energy to completely melt the solid at it's melting point, then you just need to multiply 0.438 mol * 4.700 kcal/mol to calculate how much energy is needed to melt 0.438 mol Pt. 2.06 kcal are needed.
\[85.5 g Pt*(1 mol Pt/195.1g Pt)= 0.438 mol Pt\]
\[0.438 mol Pt * 4.700 kcal/mol Pt =2.06 kcal\]

Answer 2

To be more specific, the molar enthalpy of fusion is the amount of heat required to melt 1 mol of a substance at that substances melting point.