Question

A chloride of silicon contains 79.1 mass % cl. (a) what is the empirical formula of the chloride?

Answer 1

An empirical formula is a formula that gives the proportions of the elements present in a certain compound however it does not give the actual numbers or the arrangement of the atoms. Assuming 100 grams of the compound, we determine the empirical formula as follows:

       mass      moles         

Si    20.9      0.74404       0.74404/0.74404 = 1

Cl    79.1      2.23131       2.23131/0.74404 = 2.9989

Therefore, the empirical formula would be SiCl3.

Answer 2

Answer:

SiCl₃

Explanation:

To solve this problem, let's assume that we have 100 g of that chloride of silicon. We then would have 79.1 g of Cl and 100 - 79.1=20.9 g of Si.

Then we calculate the amount of moles in the mass of each element, using the elements' atomic weight:

• 79.1 g Cl / 35.45 g·mol⁻¹ = 2.2313 mol Cl

• 20.9 g Si / 28.08 g·mol⁻¹ = 0.7443 mol Si

Now we divide the number of moles by the lowest number, in this case, it's the moles of Si:

2.2313 / 0.7443 = 2.9978 => 3

0.7443 / 0.7443 = 1

Thus the empirical formula is SiCl₃