How many moles of copper are present in a sample of tennantite with a mass of 2290 grams?

               18.58 moles of Cu

Solution:

Data Given:

                  Chemical Formula of Tennantite  =  Cu₁₂As₄S₁₃

                  Mass of Cu₁₂As₄S₁₃  =  2290 g

                  M.Mass of Cu₁₂As₄S₁₃  =  1479.06 g.mol⁻¹

Step 1: Calculate Moles of Cu₁₂As₄S₁₃ as,

                               Moles  =  Mass ÷ M.Mass

Putting values,

                               Moles  =  2290 g ÷ 1479.06 g.mol⁻¹

                                Moles  =  1.548 mol

Step 2: Calculate Moles of Cu,

As,

                         1 mole of Cu₁₂As₄S₁₃ contains  =  12 moles of Cu

So,

               1.548 mol of Cu₁₂As₄S₁₃ will contain  =  X moles of Cu

Solving for X,

                     X  =  (1.548 mol × 12 mol) ÷ 1 mol

                     X  =  18.58 moles of Cu