# Chemistry Question

Introduction to ChemistryExam III

Fall 2022

Reactions and Solutions

Name ______________________

This is an ‘At Home Exam’ due no later than Tues, Dec 6, 2022 by 11:30 p.m. on

Blackboard. Print out this exam. Neatly show all work including units and labels. Answers

with no work will only receive partial credit. If needed, use scratch paper to work out the

question and then neatly show the work in the space provided. Do not attach additional

pages. Submit this exam as one pdf. Do not submit individual pdf pages. Do not submit all

pages on one page. Submit this exam as one pdf with four consecutive pages.

You can use whatever resources needed, except:

Do not copy answers from other students in the class.

Do not ask for help at the Tutoring Center.

1.

Balance the following equations:

8 pts

a.

Cr

+

b.

Al2O3

+

c.

Fe

+

O2

d.

Au2(CO3)3

+

Cl2

H2O

CrCl3

Al(OH)3

Fe2O3

NaCl

Na2CO3

+

AuCl3

2.

Classify each of the following reactions as a combination, decomposition,

4 pts single replacement, or double replacement.

Reaction Type

a. BaCl2 (aq) + K2CO3 (aq)

b. NiCl3 (l)

BaCO3 (s) + KCl (aq

Ni (s)

+

Cl2 (g)

c. AuBr (aq) + S (aq)

Au2S (aq) +

d. CO2 (aq)

ZnCO3 (s)

+

ZnO (s)

Br2 (l)

3.

For the following Oxidation/Reduction reactions, show the two half-cells and

8 pts show which element is oxidized and which is reduced.

a.

CaSO3

b.

Pb3N2

c.

Al2O3

d.

CrN

+

+

Fe

FeSO3

FeI3

PbI4

Al

+

O2

+

+

+

Ca

Fe3N2

O2

Cr2O3

+

N2

page 2

4.

8 pts

In the following reaction, sulfur (S) reacts with aluminum chloride (AlCl3) to

produce aluminum sulfide (Al2S3) and chlorine (Cl2) gas.

3 S (s)

+

2 AlCl3 (s)

1 Al2S3 (s)

+

3 Cl2 (g)

Calculate the molar mass for the following molecules.

Show all calculations and units!

4e.

a. S

b. AlCl3

c. Al2S3

d. Cl2

How many grams of AlCl3 are consumed when 2.8 moles of Al2S3 are produced?

8 pts

4f.

If 0.75 grams of S are used, how many grams of AlCl3 are needed?

8 pts

4g.

How many grams of Cl2 is 0.15 moles of Cl2?

8 pts

4h.

With 0.67 moles of AlCl3, how many grams of Al2S3 are produce?

8 pts

page 3

5.

8 pts

6.

16 pts

Calculate the concentration of a solution when a 25 mL sample of

6 M nitric acid solution is diluted to 150 mL?

A solution is prepared by combining 8 g of sodium hydroxide (NaOH)

with 245 g of H2O and the solution has a density of 1.8 g/mL.

a. What is the mass/mass percent of the sodium hydroxide solution?

b. What is the mass/volume percent of the sodium hydroxide solution?

7.

8 pts

Calculate the milliliters of solution needed to prepare a 35% (m/v) NaOH

solution containing 27 g of NaOH.

8.

How many grams of FeCl3 are generated if 125 mL of a 0.85 M BaCl2 solution

8 pts are used in this reaction?

3 BaCl2

+

1 Fe2O3

2 FeCl3

+

3 BaO

page 4

Stoichiometry Practice Quiz

Answer Key

1. What is the molar mass for each reactant and product?

a.

FeCl3

b. BaSO4

1 x Fe = 1 x 56

= 56

3 x Cl = 3 x 35.5 = 106.5

1 x Ba = 1 x 137

1 x S = 1 x 32

4 x O = 4 x 16

162.5 g FeCl3

1 mol FeCl3

c.

= 137

= 32

= 64

233 g BaSO4

1 mol BaSO4

Fe2(SO4)3

d. BaCl2

2 x Fe = 2 x 56

= 112

3 x S = 3 x 32

= 96

12 x O = 12 x 16 = 192

1 x Ba = 1 x 137 = 137

2 x Cl = 2 x 35.5 = 71

400 g Fe2(SO4)3

1 mol Fe2(SO4)3

208 g BaCl2

1 mol BaCl2

2. Balance the equation.

2 FeCl3

+

3

à

BaSO4

1 Fe2(SO4)3

+

3 BaCl2

3. How many moles of Fe2(SO4)3 are produced when 0.0045 mol of BaCl2 are produced?

1 mol Fe2(SO4)3

3 mol BaCl2

ratio

from

chemical

equation

x

0.0045 mol BaCl2

1

=

0.0015 mol Fe2(SO4)3

4. How many moles of Fe2(SO4)3 will be produced when 145 g of BaSO4 react?

1 mol Fe2(SO 4)3

1 mol BaSO4

x

3 mol BaSO4

233 g BaSO4

ratio

from

chemical

equation

145 g BaSO4

x

1

= 0.207 mol Fe2(SO 4)3

given

molar

mass

BaSO4

5. How many grams of Fe2(SO4)3 are produced when 5.6 moles of BaCl2 are produced?

400 g Fe2(SO 4)3

x

1 mol Fe2(SO 4)3

1 mol Fe2(SO 4)3

3 mol BaCl2

5.6 mol BaCl2

x

ratio

from

chemical

equation

molar

mass

Fe2(SO 4)3

= 750 g Fe2(SO 4)3

1

given

6. How many moles of FeCl3 are in 67 grams of FeCl3?

1 mol FeCl3

162.5 g FeCl3

x

67 g FeCl3

=

0.41 mol FeCl3

1

molar

mass

FeCl3

given

7. If 4.6 grams of FeCl3 are used, how many moles of BaSO4 are needed?

3 mol BaSO4

x

2 mol FeCl3

ratio

from

chemical

equation

1 mol FeCl3

162.5 g FeCl3

molar

mass

FeCl3

x

4.6 g FeCl3

1

=

0.042 mol BaSO4

given

8. In this reaction, which element is oxidized and which is reduced?

+

Cr

à

Cr2O3

+

Zn

Zn2+ O2- +

Cro

à

Cr3+ O2-

+

Zno

Zn2+

Cro

à

Cr3+ +

Zno

(remove O2- from both sides)

Zn2+

à

Zno

(gain electrons reduction)

Cro

à

Cr3+

(lose electrons oxidation)

ZnO

+

2