   Chapter 4, Problem 103GQ

Chapter
Section
Textbook Problem

Copper metal can be prepared by roasting copper ore, which can contain cuprite (Cu2S) and copper(II) sulfide.Cu2S(s) + O2(g) → 2 Cu(s) + SO2(g)CuS(s) + O2(g) → Cu(s) + SO2(g)Suppose an ore sample contains 11.0% impurity in addition to a mixture of CuS and Cu2S. Heating 100.0 g of the mixture produces 75.4 g of copper metal with a purity of 89.5%. What is the weight percent of CuS in the ore? The weight percent of Cu2S?

Interpretation Introduction

Interpretation:

The weight percentage of CuSandCu2S in the given sample of ore has to be determined.

Concept introduction:

• For chemical reaction balanced chemical reaction equation written in accordance with the Law of conservation of mass.
• Law of conservation of mass states that for a reaction total mass of the reactant and product must be equal.

Numberofmole=GivenmassofthesubstanceMolarmass

• The molar mass of an element or compound is the mass in grams of 1 mole of that substance, and it is expressed in the unit of grams per mol (g/mol).
• Stoichiometric factor is a relationship between reactant and product which is obtained from the balanced chemical equation for a particular reaction.
• Weight percent of elements of a compound is the ratio of weight of element to the weight of whole compound and multiplied with hundred.
Explanation

Balanced chemical equation for the reaction occurred in the preparation of copper from cuprite (Cu2S) and copper (II) sulfide is,

Cu2S(s)+O2(g)2Cu(s)+SO2(g)CuS(s)+O2(g)Cu(s)+SO2(g)

Mass of impurity in the ore = 11100×100 =11g

Then the mass of CuSandCu2S is 10011=89g

Mass of Cu from CuSmassofCuSMolarmassofCuS×1molCuinCuS1molCuS×molarmassofCuS

Considering A as the mass of CuS and B as the mass of Cu2S,

Mass of Cu from CuS is,

A95.61×11×63.55g/mol=0.6626A

Similarly mass of Cu from Cu2S is,

massofCu2SMolarmassofCu2S×2molCuinCuS1molCu2S×molarmassofCu2S

Mass of Cu from Cu2S is,

B159

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