   # You are given a solid that is a mixture of Na 2 SO 4 and K 2 SO 4 . A 0.205-g sample of the mixture is dissolved in water. An excess of an aqueous solution of BaCl 2 is added. The BaSO 4 . That is formed is filtered, dried, and weighed. Its mass is 0.298 g. What mass of SO 4 2− ion is in the sample? What is the mass percent of SO 4 2− ion in the sample? What are the percent compositions by mass of Na 2 SO 4 and K 2 SO 4 in the sample? ### 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 6, Problem 129CP
Textbook Problem
191 views

## You are given a solid that is a mixture of Na2SO4 and K2SO4. A 0.205-g sample of the mixture is dissolved in water. An excess of an aqueous solution of BaCl2 is added. The BaSO4. That is formed is filtered, dried, and weighed. Its mass is 0.298 g. What mass of SO42− ion is in the sample? What is the mass percent of SO42− ion in the sample? What are the percent compositions by mass of Na2SO4 and K2SO4 in the sample?

Interpretation Introduction

Interpretation: The mass percentages in the sample have to be calculated.

Concept introduction: The mass percentage of a compound can be calculated with the calculated mass of the compound to the total mass of the compound.

Masspercent(in%)=Massofcompound(ing)Totalmass(ing)

### Explanation of Solution

Explanation

Record the given data

Mass of the sample mixture = 0.205g

Mass of the precipitate         = 0.298g

The mass of the sample mixture and mass of the precipitate are recorded as shown above.

To calculate the mass of SO42-

Molar mass of SO42- = 96.07g

Molar mass of BaSO4 = 233.4g

Mass of SO42- = 0.298gBaSO4×96.07gSO42-233.4gBaSO4

= 0.123gSO42-

The mass of SO42- is calculated by plugging in the values of mass of precipitate to the molar mass of SO42- and BaSO4 . The mass of SO42- was found to be 0.123g .

To calculate the mass percent of SO42-

Mass of SO42- = 0.123g

Mass percent of SO42- = 0.123g0.205g×100

= 60.0%

The mass percent of SO42- is calculated by plugging in the values of mass of SO42- to the total mass of the sample. The mass percent of SO42- is found to be 60.0% .

To calculate the mass of Na2SO4andK2SO4

Molar mass of K+ = 39.10g

Molar mass of Na+ = 22.99g

Assume 100.0g of Na2SO4andK2SO4 mixture there are

60.0gofSO42-=1mol96.07g=0.625molSO42-

Hence,

2×0.625=1.25molof+1cations must be present to balance 2-chargeofSO42-

Let x= mass of K+

y= mass of Na+

x+y=1.25......(1)

In 100.0g of mixture,

Total mass of K+ and Na+ = 40g. Then the equation can be given as,

xmolK+×39.10gmol+ymolNa+×22.99gmol=40.0g......(2)

Solving equation (1) and (2),

x+y=1.25g and xmolK+×39.10gmol+ymolNa+×22.99gmol=40.0g

x=1.25-ysubstitutethevalueofxin(2)39.10(1.25)y+(22.99)y=40.048.9-(39.10)y+(22.99)y=40.0-(16

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