   # Commercial brass, an alloy of Zn and Cu, reacts with hydrochloric acid os follows: Zn ( s ) + 2 HCl ( a q ) → ZnCl 2 ( a q ) + H 2 ( g ) (Cu does not react with HCl.) When 0.565 g of a certain brass alloy is reacted with excess HCl, 0.0985 g ZnCl 2 is eventually isolated. a. What .is the composition of the brass by mass? b. How could this result be checked without changing the above procedure? ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243

#### Solutions

Chapter
Section ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243
Chapter 5, Problem 148AE
Textbook Problem
1 views

## Commercial brass, an alloy of Zn and Cu, reacts with hydrochloric acid os follows: Zn ( s ) +   2 HCl ( a q ) → ZnCl 2 ( a q )   +  H 2 ( g ) (Cu does not react with HCl.) When 0.565 g of a certain brass alloy is reacted with excess HCl, 0.0985 g ZnCl2 is eventually isolated.a. What .is the composition of the brass by mass?b. How could this result be checked without changing the above procedure?

(a)

Interpretation Introduction

Interpretation: The reaction between commercial brass and hydrochloric acid is given. The composition of brass by mass is to be calculated.

Concept introduction: The mass percent of a substance in the original mixture is calculated by the formula,

Percentmass=MassofthesubstanceMassoftheoriginalmixture×100

To determine: The composition of brass by mass.

### Explanation of Solution

Given

The mass of ZnCl2 is 0.0985g .

The mass of the alloy is 0.5065g .

The molar mass of ZnCl2 =Zn+2Cl=(65.38+(2×35.5))g/mol=136.38g/mol

Formula

The number of moles of a substance is calculated by the formula,

Numberofmoles=GivenmassofthesubstanceMolarmassofthesubstance

Substitute the value of the given mass and the molar mass of ZnCl2 in the above expression.

NumberofmolesofZnCl2=0.0985g136.38g/mol=7.22×104mol

The stated reaction is,

Zn(s)+2HCl(aq)ZnCl2(aq)+H2(g)

According to the stated reaction,

1mol of Zn produces 1mol of ZnCl2 .

7.22×104mol of ZnCl2 are produced by 7.22×104mol of Zn .

The atomic mass of zinc is 65

(b)

Interpretation Introduction

Interpretation: The reaction between commercial brass and hydrochloric acid is given. The composition of brass by mass is to be calculated.

Concept introduction: The mass percent of a substance in the original mixture is calculated by the formula,

Percentmass=MassofthesubstanceMassoftheoriginalmixture×100

To determine: The authentication of the above result.

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