Question

What is the maximum number of mols of copper (III) sulfide that can be formed when 8.0 mols of copper reacts with 9.0 mols of sulfur?

Answer 1

You have to find the reaction, balance it and then compare the mole ratios.
Answer is:

`5,bar(33)g`

Explanation:

The chemical reaction is:

`4Cu+3S_2->2Cu_2S_3`

So from the left part of the equation, once can say:

For every 4 moles of copper, 3 moles of sulfur is needed.
For every 8 moles of copper, `x` moles of sulfur are needed.
For every `y` moles of copper, 9 moles of sulfur are needed.

`x=(3*8)/4=6` moles of sulfur We have 9, which is enough

`y=(4*9)/3=12` moles of copper We have 8, which is not enough

So finally, 8 moles of sulfur will react. The reaction will become:

`4Cu+3S_2->2Cu_2S_3`

`zCu+8S_2->wCu_2S_3`

`z=4*8/3=32/3`

`w=2*8/3=16/3`

`32/3Cu+8S_2->16/3Cu_2S_3`

So the maximum number moles that can be formed are:

`16/3=5,bar(33)g`