# NaCl has a DeltaH_(fus) = 30.2 kJ/mol. What is the mass of a sample of NaCl that needs 732.6 kJ of heat to melt completely?

Jun 15, 2017

$\text{559 g Na}$ would need $\text{732.6 kJ}$ of heat to melt completely.

#### Explanation:

Determine moles Na by dividing by its heat of fusion.

732.6color(red)cancel(color(black)("kJ"))xx(1"mol Na")/(30.2color(red)cancel(color(black)("kJ")))="24.3 mol Na"

Determine mass of Na by dividing by its molar mass (atomic weight in g/mol).

24.3color(red)cancel(color(black)("mol Na"))xx(22.98977"g Na")/(1color(red)cancel(color(black)("mol Na")))="559 Na" rounded to three sig figs