1. Balanced Chemical Equation:

The reaction of copper (Cu) with sulfur (S) to form copper sulfide (CuS) is:

Cu + S → CuS

This equation is already balanced.

2. Mole Ratio:

From the balanced equation, we see that 1 mole of Cu reacts with 1 mole of S to produce 1 mole of CuS.

3. Calculate Moles of Copper Sulfide:

Since you have 0.90 mol of Cu and it reacts in a 1:1 mole ratio with CuS, you will produce 0.90 mol of CuS.

4. Convert Moles to Kilograms:

* Find the molar mass of CuS:

* Cu: 63.55 g/mol

* S: 32.06 g/mol

* CuS: 63.55 + 32.06 = 95.61 g/mol

* Convert moles of CuS to grams:

* 0.90 mol CuS * 95.61 g/mol = 86.05 g CuS

* Convert grams to kilograms:

* 86.05 g CuS * (1 kg / 1000 g) = 0.08605 kg CuS

Answer: You could form 0.08605 kg of copper sulfide from the reaction of 0.90 mol of copper with excess sulfur.