Question

A sample of substance X that has a mass of 326.0 g releases 4325.8 call when it freezes at its freezing point. If substance X has a molar mass of 58.45 g/mol, what is the molar heat of fusion for substance X

Answer 1

Answer : The molar heat of fusion for substance X is, 775.6 cal/mol

Explanation :

First we have to calculate the moles of substance X.

$\text{Moles of substance X}=\frac{\text{Mass of substance X}}{\text{Molar mass of substance X}}$

Given:

Molar mass of substance X = 58.45 g/mole

Mass of substance X = 326.0 g

Now put all the given values in the above expression, we get:

$\text{Moles of substance X}=\frac{326.0g}{58.45g/mol}=5.577mol$

Now we have to calculate the molar heat of fusion for substance X.

$\Delta H=\frac{Q}{n}$

where,

Q = heat releases = 4325.8 cal

$\Delta H$ = molar heat of fusion for substance X = ?

n = moles = 5.577 mol

Now put all the given values in the above expression, we get:

$\Delta H=\frac{4325.8cal}{5.577mol}=775.6cal/mol$

Thus, the molar heat of fusion for substance X is, 775.6 cal/mol