Copper (Cu) reacts with sulfur (S) to form copper sulfide as shown in the chemical equation. A scientist adds 4 grams of Cu to 2 grams of S to start the reaction. At the end of the experiment, she has 6 grams of product. In one to two sentences, explain what would happen if the scientist increased the amount of copper to 6 grams, and why.

Explanation:

         Cu     + S     =     CuS .

   4 grams of copper = 4 / 63.5 = .0629

2 grams of sulphur = 2 / 32 = .0625  

So .0629 mole of copper reacts with same mole of sulphur

So the reaction is taking place  as follows

Cu     + S     =     CuS .

If copper is increased to 6 grams

6 gm of copper = 6 / 63.5 = .0944 moles of copper

sulphur =  .0625   moles

ratio of moles of copper and sulphur =  .0944 / .0625 = 3 / 2 = 1.5

Another compound may be formed as follows

3 Cu + 2 S = Cu₃ S₂

Compound between copper and sulphur can be formed in many ratios where the ratio of cu and s can vary between .5 to 2 . Hence in this case compound like Cu₃S₂ may be formed.