1. Assume a 100g Sample

* This makes the calculations easier, as the percentages directly translate to grams.

* We have 55.6 g of calcium (Ca) and 44.4 g of sulfur (S).

2. Convert Grams to Moles

* Divide the mass of each element by its molar mass:

* Moles of Ca = 55.6 g / 40.08 g/mol = 1.387 mol

* Moles of S = 44.4 g / 32.06 g/mol = 1.385 mol

3. Determine the Mole Ratio

* Divide both mole values by the smaller value (1.385 mol) to get the simplest whole-number ratio:

* Ca: 1.387 mol / 1.385 mol ≈ 1

* S: 1.385 mol / 1.385 mol ≈ 1

4. Write the Formula

* The mole ratio indicates that there is one calcium atom for every one sulfur atom.

* Therefore, the formula of the compound is CaS.

The compound is Calcium Sulfide (CaS).