Answer to Question #167311 in Chemistry for Emily

Question

CuO can be formed from the reaction of 18.7g of CuS and 12.0g of O2. Which reactant will run out first

Answer 1

Solution:

The balanced chemical equation:

2CuS + 3O₂ → 2CuO + 2SO₂

According to the equation above: n(CuS)/2 = n(O₂)/3

Determine moles of each reactant:

18.7 g CuS × (1 mol CuS / 95.611 g CuS) = 0.1956 mol CuS

12.0 g O₂ × (1 mol O₂ / 31.998 g O₂) = 0.3750 mol O₂

Choose one reactant and determine how many moles of the other reactant are necessary to completely react with it. Let's choose CuS:

n(O₂) = 3 × n(CuS) / 2 = (3 × 0.1956 mol) / 2 = 0.2934 mol

The calculation above means that we need 0.2934 mol of O₂ to completely react with CuS.

We have 0.3750 mol of O₂ and therefore more than enough oxygen.

Thus oxygen (O₂) is in excess and copper monosulfide (CuS) must be the limiting reagent.

Hence, CuS will run out first.

Answer: CuS will run out first.