Answer to Question #169352 in Chemistry for Emily

Question

What mass of CuO can be formed from the reaction of 8.35g of CuS and 7.20g of O2

Answer 1

Solution:

The balanced chemical equation:

2CuS + 3O₂ → 2CuO + 2SO₂

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

Let's start by converting the masses of CuS and O₂​ to moles using their molar masses:

8.35 g CuS × (1 mol CuS / 95.611 g) = 0.08733 mol CuS

7.20 g O₂​ × (1 mol O₂​ / 31.9988 g) = 0.2250 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 × 0.08733 mol) / 2 = 0.130995 mol​

The calculation above means that we need 0.130995 mol of O₂ to completely react with CuS.

We have 0.2250 mol of O₂ and therefore more than enough oxygen.

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

Thus: n(CuO) = n(CuS) = 0.08733 mol

Moles of CuO = Mass of CuO / Molar mass of CuO

Mass of CuO = Moles of CuO × Molar mass of CuO

The molar mass of CuO is 79.545 g mol^-1.

Hence,

Mass of CuO = 0.08733 mol × 79.545 g mol^-1 = 6.9466 g = 6.95 g

Mass of CuO = 6.95 g

Answer: 6.95 grams of CuO can be formed.