Question

The mineral greenockite is a yellow sulfide of cadmium that is 78.0% cadmium and 22.0% sulfur. Determine the empirical formula of greenockite.

Answer 1

Answer:

CdS

Explanation:

We are given;

• % of cadmium is 78%
• % of sulfur is 22.0%

We are required to determine the empirical formula of cadmium sulfide

Step 1 : Determine the number of moles of Cadmium and sulfur

Assuming the mass of the cadmium sulfide is 100 g

Mass of cadmium is 78 g

Mass of sulfur is 22 g

But;

Moles = Mass ÷ Molar mass

Molar mass of Cadmium = 112.411 g/mol

Moles of Cadmium = 78 g ÷ 112.411 g/mol

                               = 0.694 moles

                              = 0.69 moles

Molar mass of sulfur is 32.065 g/mol

Moles of sulfur = 22 g ÷ 32.065 g/mol

                         = 0.686 moles

                       = 0.69 moles

Step 3: Determine the whole number mole ratio of Cadmium to sulfur

Cadmium : Sulfur

          Cd  :  S

   0.69 moles : 0.69 moles

  0.69/0.69  : 0.69/0.69

                   1 : 1

Therefore, the empirical formula of greenockite is CdS