Question

binary compound created by reaction of an unknown element E and sulfur contains 27.52% E and 72.48% S by mass. If the formula of the compound is E4S10, calculate the atomic mass of E.

Answer 1

Answer : The atomic mass of E is, 30.4 g/mol

Explanation :

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of E = 27.52 g

Mass of S = 72.48 g

First we have to calculate the moles of sulfur.

Moles of S = $\frac{\text{ given mass of S}}{\text{ molar mass of S}}= \frac{72.48g}{32g/mole}=2.265moles$

Now we have to calculate the moles of E by comparing the stoichiometry of the compound.

The given compound formula is, $E_4S_{10}$

As, 10 moles of sulfur combine with 4 moles of E

So, 2.265 moles of sulfur combine with $\frac{2.265}{10}\times 4=0.906$ moles of E

Thus, the moles of E is, 0.906 moles.

Now we have to calculate the atomic mass of E.

Atomic mass of E = $\frac{\text{ given mass of E}}{\text{ moles of E}}= \frac{27.52g}{0.906mole}=30.4g/mol$

Thus, the atomic mass of E is, 30.4 g/mol