Question

A compound of sulfur and oxygen is 50.0% sulfur, 50.0% oxygen by weight. Sulfur and oxygen form another compound, in accordance with the law of multiple proportions. Which of the following is a likely composition for the second compound?

a) 85.0 mass % sulfur 15.0 mass % oxygen.
b) 65.0 mass % sulfur 35.0 mass % oxygen.
c) 55.0 mass % sulfur 45.0 mass % oxygen.
d) 45.0 mass % sulfur 55.0 mass % oxygen.
e) 40.0 mass % sulfur 60.0 mass % oxygen.

Answer 1

e) 40.0 mass % sulfur & 60.0 mass % oxygen.

Step-by-step explanation:

Let's assume we have 100 g of the compound, we would have 50 g of O and 50 g of S.

Converting masses to moles:

50 g O ÷ 16 g/mol = 3.125 mol O

50 g S ÷ 32 g/ mol = 1.5625 mol S

Now we determine the empirical formula for that compound, to do that we divide the moles by the lowest number among them:

O ⇒ 3.125 / 1.5625 = 2

S ⇒ 1.5625 / 1.5625 = 1

So the empirical formula is SO₂

Another S and O compound is SO₃, which contains 32 g of S and (16x3) 48 g of O. That's a 40:60 ratio.