Copper(ii) sulfide is formed when copper and sulfur are heated together. in this reaction,
54 g of copper reacts with 42 g of sulfur. what is the mass of copper(ii) sulfide formed?

The mass of copper(II) sulfide formed is:

= 81.24 g

Explanation:

The Balanced chemical equation for this reaction is :

given mass= 54 g

Molar mass of Cu = 63.55 g/mol

Moles of Cu = 0.8497 mol

Given mass = 42 g

Molar mass of S = 32.06 g/mol

Moles of S = 1.31 mol

Limiting Reagent : The reagent which is present in less amount and consumed in a reaction

First find the limiting reagent :

1 mol of Cu require = 1 mol of S

0.8497 mol of Cu should require  = 1 x 0.8497 mol

= 0.8497 mol of S

S present in the reaction Medium = 1.31 mol

S Required  = 0.8497 mol

S is present in excess and Cu is limiting reagent

All Cu is consumed in the reaction

Amount Cu will decide the amount of CuS formed

1 mole of Cu  gives = 1 mole of Copper sulfide

0.8497 mol of Cu =  1 x 0.8497 mole of Copper sulfide

= 0.8497

Molar mass of CuS = 95.611 g/mol

Mass of CuS = 0.8497 x 95.611

= 81.24 g

the answer to this question is 3.