CHEM1010_ppt_Ch_08

CHEM1010 Ch 8 1

Example: combustion of propane

C3H8(g) + O2(g) CO2(g) + H2O(g)

The physical state (the part in parentheses) are important because it will help us determine what is happening.

Abbreviation State

g gas

l liquid

s solid

aq aqueous

Writing Chemical Equations

CHEM1010 Ch 8 2

Example:

Mixing aqueous calcium bromide and aqueous silver nitrateto produce aqueous calcium nitrate and solid silver bromide


CHEM1010 Ch 8 3

Many substances you should know the physical state of (at room temperature), such as

• gases: O2, H2, CO, CO2

• liquids: H2O

• solids (we will be talking about solubility rules)

For the most part, however, you will have to be told the physical state.

For example: Iodine is a solid at room temperature

Write this example.


CHEM1010 Ch 8 4

Writing Chemical Equations Homework:

Chapter 8 Exercises: 7, 9, 11, 13, 15

CHEM1010 Ch 8 5

Always balance a chemical equation before starting any problem!!!

A chemical equation is like a recipe. You need to know the ratio of ingredients and products or you will end up with the wrong answer.

If you wanted to make 7 cakes, you would need to know how many eggs and how much oil you would need per cake or you wouldn’t know how much of

each you needed to complete your project.

CakeMix

Balancing Chemical Equations

CHEM1010 Ch 8 6

Always balance a chemical equation before starting any problem!!!

Hints:• Start with least occurring atoms but largest number of atoms

• Place coefficient in front of molecule, including 1’s

Example: combustion of propane

C3H8(g) + O2(g) CO2(g) + H2O(g)

For now, ignore the phases (the part in parentheses).


CHEM1010 Ch 8 7



Ca(OH)2 + HCl CaCl2 + H2O

N2 + H2 NH3

P + Cl2 PCl3

Na + Cl2 NaCl

C7H5N3O6 N2 + CO + H2O + C

Fe + O2 Fe2O3

O2 O3

H2 + O2 H2O


CHEM1010 Ch 8 8



Ca(OH)2 + HNO3 Ca(NO3)2 + H2O

MgO + HNO3 Mg(NO3)2 + H2O

HI + Mg(OH)2 MgI2 + H2O

CaCO3 + HBr CaBr2 + CO2 + H2O

Mixing calcium bromide and silver nitrateto produce calcium nitrate and silver bromide


CHEM1010 Ch 8 9

Balancing Chemical Equations Homework:

Chapter 8 Exercises: 17 – 20Note: Answers to 17e and 19a are incorrect in the back of the book. See homework answers for these problems.

CHEM1010 Ch 8 10

Type of Reaction Generic Equation

Combination A + B → AB

Decomposition AB → A + B

Displacement A + BC → AC + B

Double-displacement AB + CD → AD + CB

Oxidation-Reduction (none)

A reaction can fall into at most one of these 4 types of reactions.

However, it can be an oxidation-reduction reactionand also fall into one of these 4 categories.

Classifying Chemical Equations

Combination

CHEM1010 Ch 8 11

Oxidation-Reduction Reactions







We will first study how to tell it is an oxidation-reduction (redox) reaction. We will study more about

oxidation-reduction reactions later.

Biochemistry:Oxidation-reduction reactions are very important.You have probably heard about “anti-oxidants”.


CHEM1010 Ch 8 12







Oxidation-reduction (redox) involves the transfer of electrons.There is always a transfer of electrons when an element goes from

an elemental form (no charge) to being in a compound (or vice versa).

For example in the combustion of methane:CH4 + 2 O2 CO2 + 2 H2O

What tips you off that this is a redox reaction?


Oxidation-Reduction Reactions

________________

CHEM1010 Ch 8 13

Which of the following reactions are redox reactions?

a) 2 Na + Cl2 2 NaCl

b) Ag+ + HCl AgCl + H+

c) CaCO3 + Sr SrCO3 + Ca

d) BaCl2 + H2SO4 BaSO4 + 2 HCl


CHEM1010 Ch 8 14

Which of the following reactions are redox reactions?

a) Mg(OH)2 + 2 H+ Mg2+ + 2 H2O

b) 2 H2O + O2 2 H2O2

c) When acid (HCl) is added to aluminum, the aluminum dissolves and forms aluminum chloride.

Hydrogen gas is given off.


CHEM1010 Ch 8 15

Combination Reaction

Displacement Reaction

Decomposition Reaction

Double-displacement Reaction








Combination

CHEM1010 Ch 8 16







Combines to form only one product

Examples:2 H2 + O2 2 H2O2 SO2 + O2 2 SO3

SO3 + H2O H2SO4


CHEM1010 Ch 8 17


In Biochemistry: Hemoglobin (in the lungs)

hemoglobin

O2

hemoglobin

O2







FYI

CHEM1010 Ch 8 18






One reactant breaking down into smaller products

Examples:


2 H2O 2 H2 + O2

electolysis

2 HgO 2 Hg + O2

∆

CaCO3 CaO + CO2

∆


CHEM1010 Ch 8 19

One reactant breaking down into smaller products


In Biochemistry: Hemoglobin (in the cells)

hemoglobin

O2

hemoglobin

O2







FYI

CHEM1010 Ch 8 20






One element displaces another element:Always one neutral element present both

before and after

Examples:

2 Na + 2 H2O 2 NaOH + H2

Zn + Cu(NO3)2 Zn(NO3)2 + Cu



DisplacementSingle Displacement

ReplacementSingle Replacement

CHEM1010 Ch 8 21


In Biochemistry, single displacement is sometimes referring to a broader and more complex definition. While we will stick to the above definition, what we do in

this class will be a good introduction to biochemistry and the displacement of substrates in enzymes.







FYI

CHEM1010 Ch 8 22






Trading partners

Examples:

HCl + NaOH NaCl + H2OBa(NO3)2 + K2SO4 BaSO4 + 2 KNO3

3 K2S + 2 FeCl3 Fe2S3 + 6 KCl



Double DisplacementMetathesis

ions

CHEM1010 Ch 8 23


Biochemistry: Neutralizing stomach acid with bicarbonateHCl + NaHCO3 NaCl + H2CO3

H2CO3 H2O + CO2

H+

HCO3–

CO2

H2O

Classify the 2nd reaction.






Classifying Chemical Equations FYI

CHEM1010 Ch 8 24







CombinationCombination

Oxidation-Reduction


CHEM1010 Ch 8 25

Classify the following reactions:

a) 2 Na + Cl2 2 NaCl

b) Ag+ + HCl AgCl + H+

c) CaCO3 + Sr SrCO3 + Ca

d) BaCl2 + H2SO4 BaSO4 + 2 HCl








CHEM1010 Ch 8 26

Classify the following reactions:

a) Mg(OH)2 + 2 H+ Mg2+ + 2 H2O

b) 2 H2O + O2 2 H2O2

c) When acid (HCl) is added to aluminum, the aluminum dissolves and forms aluminum chloride.

Hydrogen gas is given off.








CHEM1010 Ch 8 27

Classifying Chemical Equations Homework:

Chapter 8 Exercises: none

Additional Exercises:

a1) Classify each reaction in exercise 17 as combination, decomposition, single-replacement, double-displacement and/or redox.




CHEM1010 Ch 8 28

Why is it that . . .

Activity Series

. . . when magnesium or zinc is placed in acid,it dissolves (producing hydrogen gas) . . .

. . . BUT when gold is placed in acid,

it does NOT dissolve (no hydrogen gas

produced)?

Answer: the Activity Series!!!

CHEM1010 Ch 8 29

HCl + Mg →

HCl + Au →

LiKBaSrCaNaMgAlMnZnFeCdCoNiSnPb(H)CuAgHgAu

Activity Series

Predict the products:

Assume that, if there is a reaction,that Magnesium goes to Magnesium (II).

Unless you are told otherwise, assume that metals go to their most common oxidation state.

CHEM1010 Ch 8 30

Should you wear jewelry in the laboratory where there are acids?


Acids with Gold (Au):

Gold: Reactivity is low

• Gold-plated (over copper, silver, ?)

• Gold-filled (brass = copper & zinc)

Acids with Metals:

Working in the laboratory –

Something to think about!

Activity Series

CHEM1010 Ch 8 31

•Acids with Metals


Pennies minted after 1982:

Mixture of copper and zinc.

Activity Series

CHEM1010 Ch 8 32

Predict the products:

a) HCl + Zn →

b) Ag + HBr →

c) Al + HBr →


Activity Series

CHEM1010 Ch 8 33


Activity Series

Why is it that zinc in an aqueous lead solutionreacts to give a gray deposit of spongy Pb metal?

Zn(s) + Pb(NO3)2(aq) →

Pb(s) + Zn(NO3)2(aq)

Note that the zinc metal (solid) is dissolving and the

lead metal (solid) is forming.

CHEM1010 Ch 8 34

Predict the products (if any):Note: IF Mn reacts, assume it forms Mn+2

a) Mn + Ni+2 →

b) Mn + Mg+2 →

c) Fe(s) + MgCl2(aq) →

d) Fe(s) + Pb(NO3)2(aq) →


Activity Series

Classify the above reactions.

CHEM1010 Ch 8 35

Why doesn’t the copper and zinc react?

Pennies minted after 1982:

Mixture of copper and zinc.


Activity Series

http://en.wikipedia.org/wiki/File:2005_Penny_Obv_Unc_D.png

CHEM1010 Ch 8 36

Activity Series Homework:

Chapter 8 Exercises: 47, 49, 51, 53, 55, 57

CHEM1010 Ch 8 37

Solubility Rules for Ionic Compounds

Some salts dissociate in waterNaCl (s) Na+ (aq) + Cl– (aq)

and they dissolve.

How can you tell which will happen?Solubility Rules!

Some salts are insolubleAg+ (aq) + Cl– (aq) AgCl(s)

and they form a precipitate.

http://en.wikipedia.org/wiki/File:Iv1-07_014.jpg

CHEM1010 Ch 8 38

Solubility Rules: Part I: Generally SolubleCompounds containing the following ions are generally

soluble in water:1) alkali metal ions and the ammonium ion2) acetate ion3) nitrate ion4) halide ions

(AgX, Hg2X2 and PbX2 are insoluble exceptions)5) sulfate ion

(SrSO4, BaSO4 and PbSO4 are insoluble exceptions)


CHEM1010 Ch 8 39

Solubility Rules: Part II: Generally InsolubleCompounds containing the following ions are generally

insoluble in water:6) carbonate ion (see rule 1 exceptions which are soluble)7) chromate ion (see rule 1 exceptions which are soluble)8) phosphate ion (see rule 1 exceptions which are soluble)9) sulfide ion (CaS, SrS, BaS and rule 1 exceptions which are soluble)10) hydroxide ion [Ca(OH)2, Sr(OH)2, Ba(OH)2 and rule 1 exceptions

that are soluble]


CHEM1010 Ch 8 40


soluble in water:1) alkali metal ions and the ammonium ion

For determining solubility, first check the cation.•If this rule applies, it is soluble.

•If this rule does not apply, continue down the rules to find the rule for the anion to determine if it is soluble.


CHEM1010 Ch 8 41



It is worth memorizing that Na+, K+ and NH4+ are always soluble.

Biochemistry ExampleNa+ and K+ play important roles in the cells.

There are sodium-potassium pumps that involve moving these ions across the cell membrane.

Why is it important that sodium and potassium salts are soluble?


CHEM1010 Ch 8 42



For each of the following, determine if this rule makes the compound soluble. If this rule does not apply to the

compound, tell what anion you need to check the solubility of.a) Na3PO4

b) NH4NO3

c) Fe2S3

d) BaSO4

e) BaCO3


CHEM1010 Ch 8 43

Determine what each solid will do in the presence of water

Out of water In water Visualization in water

NaCl (s) KNO3 (s) CuCl2 (s) BaCO3 (s)

Fe3(PO4)2 (s) AgOH(s)


CHEM1010 Ch 8 44

Why do they use BaSO4 and not BaCO3 in upper GI’s?

BaSO4 and BaCO3 are both ______________However, this is in ______________

In acid, carbonates are soluble:BaCO3(s) + H+(aq) → Ba2+(aq) + H2O(l) + CO2(g)

Sulfates are insoluble:BaSO4 (s) → no reaction

This is very important because barium is toxic

So, why do they use BaSO4 and not BaCO3 in upper GI’s?

Solubility Rules for Ionic Compounds FYI

CHEM1010 Ch 8 45

Solubility Rules for Ionic Compounds Homework:

Chapter 8 Exercises: 67 – 70

CHEM1010 Ch 8 46

1) A precipitate (insoluble substance) forms.

2) Water forms.

3) A gas forms.

Double-Replacement Reactions

We can write a reaction but it doesn’t mean that it will really happen.We will study 3 different reasons a reaction would happen:

CHEM1010 Ch 8 47

Double replacement reactions:A reaction will occur if:

1) the reactants are soluble2) at least one product must precipitate

Precipitous Reactions

CHEM1010 Ch 8 48

We will only be looking at double replacement reactions

for ionic compounds.

For example:KI(aq) + Pb(NO3)2(aq) →

KNO3(aq) + PbI2(s)

Draw a picture showing how they would exist in water.As they float around in the water, what would happen?


CHEM1010 Ch 8 49

We will only be looking at double replacement reactionsfor ionic compounds.

In order for a reaction to occur,1) the reactants must be soluble

2) at least one product must precipitate

Do that for our previous example and include the physical states:

Rather than draw pictures, we will just “trade partners” and see if a precipitate forms.


KI + Pb(NO3)2 →

CHEM1010 Ch 8 50

NaCl + KI →

“Trade partners” for this example and see if a precipitate forms. (Include physical states.)


Draw a picture showing how they would exist in water.As they float around in the water, what would happen?

CHEM1010 Ch 8 51

Determine if the following will react.If they do react, write the products.If they do not react, write “NR”.

a) Na3PO4 + Pb(NO3)2 →

b) Pb3(PO4)2 + FeCl2 →

c) Ca(NO3)2 + Na2SO4 →

d) NaOH + HgSO4 →

e) Na2CO3 + CaCl2 →

f) KNO3 + MgCl2 →

g) MgCl2 + KOH →

h) NH4Cl + K2SO4 →

i) Na2S + CuSO4 →

j) NaOH + HI →


CHEM1010 Ch 8 52

Precipitous Reactions Homework:

Chapter 8 Exercises: 71 – 74

Additional Exercises:Write a molecular equation for the precipitation (if any) that occurs when the following are mixed. If no reaction occurs, write “NO REACTION”.a5) sodium carbonate and lead(II) nitratea6) potassium sulfate and lead(II) acetatea7) copper(II) nitrate and barium sulfidea8) calcium nitrate and sodium iodidea9) barium nitrate and ammonium sulfatea10) barium sulfide and potassium chloridea11) sodium acetate and lead(II) nitrate

CHEM1010 Ch 8 53


2) Water forms.

3) A gas forms.



CHEM1010 Ch 8 54

Acid-Base reactions always react, even if they do not produce a solid or a gas. They neutralize each other.

For now, we will start with a very simple definition of acids and bases.

We will later recognize this as the Arrhenius definition of acids and bases.

H+ + OH− → H2O(l)

Acid – produces H+ ions in aqueous

solution.

Base – produces OH− ions in aqueous

solution.

Neutralization Reactions

CHEM1010 Ch 8 55

Acid-Base reactions always react, even if they do not produce a solid or a gas. They neutralize each other.

H+ + OH− → H2O(l)

Acid

Base


Water

CHEM1010 Ch 8 56

Acid-Base reactions always react, even if they do not produce a solid or a gas.

They neutralize each other.

H+ + OH− → H2O(l)

In fact, this reaction is so strong, the acid and base do not even

have to be aqueous. An acid will dissolve any base, even if it isn’t

soluble (i.e. aqueous).

HNO3(aq) + Al(OH)3(s) → H2O(l) + Al(NO3)3(aq)


HNO3(aq)

Al(OH)3(s)

Al(NO3)3(aq)

CHEM1010 Ch 8 57

Review:In the above reaction:

a) which is the acid and how do you know it’s an acid?b) which is the base and how do you know it’s a base?

HNO3(aq) + Al(OH)3(s) → H2O(l) + Al(NO3)3(aq)


CHEM1010 Ch 8 58

In the above reaction:How would we predict the products?

HNO3(aq) + Al(OH)3(s) →


CHEM1010 Ch 8 59

a) HNO3 + Pb(OH)2 →

b) HNO3 + Ba(OH)2 →

c) H2SO4 + NaOH →

d) H3PO4 + Ba(OH)2 →

e) KOH + H2SO4 →

f) NaCl + H2SO4 →

g) NaOH + KOH →

Complete and balance each of the following reactions.(Be sure to include the physical state – s, l, g, or aq)


CHEM1010 Ch 8 60

Neutralization Reactions Homework:

Chapter 8 Exercises: 76, 78NOTE: Tests will require that water is written as H2O, NOT HOH.

Additional Exercises:a12) Write a molecular equation for the reaction (if any) that occurs when the following are mixed: chromium(III) hydroxide and nitric acid (HNO3) Be sure to include the physical state (s, l, g, or aq) of both the reactants and products.

NOTE: Tests will require that water is written as H2O, NOT HOH

The textbook sometimes writes water as HOH.

CHEM1010 Ch 8 61


2) Water forms.

3) A gas forms.



CHEM1010 Ch 8 62

We can predict that an aqueous reaction will occur whenever a gas is formed because the gas escapes.

So, when at double replacement reaction produces a gas, we can predict the reaction will occur.

Let’s look at some reactions that produce gases.

Gas Evolving Reactions

CHEM1010 Ch 8 63

We can predict that an aqueous reaction will occur whenever a gas is formed because the gas escapes.

For example, when H2S is formed, it is a gas.

HNO3 + BaS →


(Note: If a test question requires knowing H2S is a gas, you will be given that information.)

CHEM1010 Ch 8 64

When carbonic acid is formed (H2CO3) it is not a gas but it decomposes into water and carbon dioxide (a gas).

(Memorize this.)

HCl + Na2CO3 →double displacement

Decomposition

Predict the products in the above reaction.

NaCl + H2CO3 → NaCl + H2O + CO2


CHEM1010 Ch 8 65

Biochemistry: Neutralizing stomach acid with bicarbonateHCl + NaHCO3 NaCl + H2CO3

H2CO3 H2O + CO2

H+

HCO3–

CO2

H2O

The body also uses bicarbonate to neutralize stomach acid before entering the intestines.

FYIGas Evolving Reactions

CHEM1010 Ch 8 66

When ammonium hydroxide is formed (NH4OH) it is not a gas but it decomposes into

water and ammonia (a gas).(Memorize this.)

NaOH + NH4Cl →double displacement

Decomposition


Predict the products in the above reaction.

NaCl + NH4OH → NaCl + H2O + NH3

CHEM1010 Ch 8 67

Biochemistry:Ammonia is produced in the liver, intestines, and kidneys

as an end product of protein metabolism.The liver converts ammonia into urea,which is then excreted by the kidneys.

Many people still refer to ammonia (NH3) in water as ammonium hydroxide (NH4OH). You just have to be aware of this as you read different sources.

FYIGas Evolving Reactions

Ammonia levels in the blood rise when the liver is not able to convert ammonia to

urea. This may be caused by cirrhosis or severe hepatitis.

http://simplyrecipes.com/recipes/liver_and_onions/

CHEM1010 Ch 8 68

Given that dihydrogen sulfide is a gas,:Complete and balance the following reactionsif the reaction occurs. (Otherwise write NR.)

a) HNO3 + NaHCO3 →

b) KNO3 + Ba(OH)2 →

c) H2SO4 + Li2S →

d) (NH4)3PO4 + Ba(OH)2 →

e) Ca(OH)2 + K2S →


CHEM1010 Ch 8 69

Gas Evolving Reactions Homework:

Chapter 8 Exercises: none

Additional Exercises:Write a molecular equation for the reaction (if any) that occurs when the following are mixed.Be sure to include the physical state (s, l, g, or aq) of both the reactants and products.a13) HCl + KHCO3

a14) HNO3 + K2CO3

a15) CaS + HNO3

a16) NH4NO3 + Ca(OH)2

a17) SrS + HCl

General Exercises: 81, 83, 85, 87Self-Test Exercises: 2 – 4, 9 – 18

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CHEM1010_ppt_Ch_08