Chemical Reactions Balance Equation
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Chemical Reactions Balance Equation

Double-displacement Reaction: . Precipitation. acid-base neutralization. gas-evolving. Single-displacement Reaction. 2. 2. Experiencing Chemical Change. Chemical Reactions. : happening both around you and in you all the time! .

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Chemical Reactions Balance Equation




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Presentation on theme: "Chemical Reactions Balance Equation"— Presentation transcript:

Slide1

Chemical Reactions

Balance Equation

Double-displacement Reaction:

Precipitation

acid-base neutralization

gas-evolving

Single-displacement Reaction

Slide2

2

2

Experiencing Chemical Change

Chemical Reactions

: happening both around you and in you all the time!

 + 

some are very simple, others are complex

involving changes in the structures of the molecules

many times we can experience the effects of those changes

Chemical reactions you experience?

Combustion of gasoline/natural gas

Seasonal color change of leaves

Bleaching of laundry

Slide3

3

3

Chemical Reactions

Chemical changes: New matter forms

Rearrangement and exchange of atoms

to produce new molecules

Elements are not transmuted

A reaction resemble life cycles

(at 1:45)

Reactants

Products

Slide4

4

4

Chemical Equations:

Conservation of Mass

Matter cannot be created or destroyed

Total

mass

cannot change

Total mass of the reactants will be the same as the total mass of the products:

Mass

Reactant =

Mass ProductAll the atoms present at the beginning are still present at the end: #Atom X (Reactant) = #Atom X (Product)if all the atoms are still there, then the mass will not change

Slide5

5

5

Components in Chemical Equations:

2Mg(s) + O

2

(g)

®

2MgO(s)

Shorthand way of describing a reaction

Provides information about the reaction

Formulas of Reactants (

Left) and Products (Right)States of Reactants and Products in “( )”. (solid/liquid/gas)Relative #Reactant and #Product molecules (Coefficients)

Slide6

6

6

Symbols Used in Equations

Indicating the

state

after chemical

(g) = gas; (

l

) = liquid; (s) = solid

(aq) = aqueous = dissolved in water

energy symbols used above the arrow for decomposition reactions

D = heat hn = light shock = mechanicalelec = electrical

Slide7

7

7

Combustion of Methane:

Balanced!

To obey the Law of Conservation of Mass, the equation must be

balanced

CH

4

(g) +

2 O

2(g)

® CO2(g) + 2 H2O(g)

H

H

C

H

H

+

O

O

C

+

O

O

O

O

+

O

H

H

O

H

H

+

1 C + 4 H + 4 O

1 C + 4 H + 4 O

Slide8

8

8

Balance Table

For a balanced equation, there are

equal

numbers of atoms of each element on the Reactant and Product sides

to obtain the number of atoms of an element, multiply the

subscript

by the

coefficient

1

 C  14  H  4 4  O  2 + 2

CH

4

(g) +

2

O

2

(g)

®

CO

2

(g) +

2

H

2

O(g)

Slide9

9

9

How to Write & Balance Chemical Equation

Skeletal

equation

Balance table: Polyatomic ions as one “

Group

”.

3. Pick an element to balance:

Pick

Element/Group w/ highest #Atoms

Find the Least Common Multiple Multiply each count by a factor to equal the LCM. Recount and Repeat until Balanced.

__CH

4

O(g) + __O

2

(g)

®

__CO

2

(g) +

__

H

2

O(g)

Slide10

10

10

Example

Solid aluminum react with aqueous sulfuric acid to form aqueous aluminum sulfate and hydrogen gas

Write a

skeletal

equation.

Count

#Atom

or #

Groups

Setup balancing table and balance. Don’t start with elements in more than one formulaFind the Least Common Multiple of the number of atoms on each side.

Slide11

11

11

Example: Balance as Ions

Fe(CN)

3

(s) + H

2

SO

4

(

aq

) ® Fe2(SO4)3(aq) + HCN(aq)____ and ____ are groups

Slide12

12

12

Example: Balance equation

C

8

H

18

+ O

2

®

CO2 + H2O

Slide13

13

Practice: Balancing Equations

C

12H22O11 + O2  CO2 + H2 O

(NH

4

)

3

PO

4 + Ca(NO

2)

2  Ca3(PO4)2 + NH4NO2

Slide14

14

Classifying Reactions

A. based on the process that happens (we observes)

precipitation, neutralization, formation of a gas, or transfer of electrons

Slide15

15

Classifying Reactions

B. by what the atoms and/or ions do (at molecular/atomic level)

Type of ReactionGeneral Equation

Synthesis

A + B

 AB

Decomposition

AB

 A + B

Displacement

A + BC

 AC + B

Double Displacement

AB + CD

 AD + CB

Slide16

16

16

Predicting Whether a Reaction Will Occur in Aqueous Solution

“Forces” that drive a reaction

formation of a solid (aka “Precipitation”)

formation of water

formation of a gas

transfer of electrons

when chemicals (dissolved in water) are mixed and one of these 4 things can occur, the reaction will generally happen

Slide17

17

Double Displacement Reactions

Exchange ionic partners:

AB + CD  AD + CBExample: Iron(III) nitrate + sodium sulfide  Iron(III) __________ + sodium __________Double displacement reaction occurs when forming Precipitation Water (Acid-base neutralization reaction)Gas (one of the products to make a gas)

Slide18

18

18

Reactions in Aqueous Solutions

Often the chemicals we are reacting together are dissolved in water

Aqueous solutions

= mixtures of a chemical dissolved in water

Dissolving the chemicals in water helps them to react together

faster

Water molecules separate the chemicals into individual

molecules or ions

The free floating particles

collide more frequently so the reaction speeds up

Slide19

19

19

Dissociation of Ionic Compound

D

issociation

:

When ionic compounds dissolve in water, the

anions

and

cations

are

separated from each other - however not all ionic compounds are soluble in water!When compounds containing polyatomic ions dissociate, the polyatomic group stays together as one ion

Slide20

20

20

Dissociation of Ionic Compounds

Potassium iodide

potassium cations and iodide anions: KI(aq)

K

+

(aq) + I-

(aq)

Copper(II) sulfate  copper(II) cations and sulfate anions: CuSO4(aq)  Cu2+(aq) + SO42-(aq)

K

+

I

-

K

I

Cu

2+

SO

4

2-

Cu

SO

4

Slide21

21

21

Polyatomic Ionic Compounds

Ammonium sulfate

ammonium cations and sulfate anions

(NH

4

)

2SO

4(aq

)  2 NH4+(aq) + SO42-(aq)

SO

4

2-

NH

4

+

SO

4

NH

4

+

NH

4

+

NH

4

+

Slide22

22

Practice: How Ionic Compounds Dissociate?

Ammonium phosphate

Cobalt(III) sulfateZinc bromide

Slide23

23

Formation of Precipitation Depends on the Solubility of Ionic Compound

a compound is

soluble in a liquid if it dissolves in that liquid. It almost completely dissociate into ions.NaCl is soluble in watera compound is insoluble if a significant amount does NOT dissolve in that liquid. It essentially does NOT dissociate into ions.CaCO3(marble stone) is insoluble in waterthough there is a very small amount dissolved, but not enough to be significant

Slide24

24

24

How to Predict the Solubility of Ionic Compound?

Predicting whether a compound will dissolve in water is not easy

Such knowledge comes through Experimentation:

Do some Experiments to test whether a compound will dissolve in water

Then develop some rules based on those experimental results

we call this method the

Empirical method

Slide25

25

Compounds Containing the following Ions are Generally Soluble

Exceptions

(insoluble when combined with ions on the left)

Li

+

, Na

+

, K

+

, NH

4+;H+ (most acids in this class)

none

NO

3

, C

2

H

3

O

2

, ClO

4

None

Cl

, Br

, I

Cu

+

,

Ag

+

,

Hg

2

2+

,

Pb

2+

(

CI

S

MI

LE

)

SO42–

Ag+, Ca2+, Sr2+, Ba2+

, Pb

2+Solubility Rule. Part I Compounds that are Generally Soluble in Water

Slide26

26

26

Compounds Containing the following Ions are Generally Insoluble

Exceptions

(when combined with ions on the left the compound is soluble or

slightly soluble

)

OH

(hydroxide, base)

Li

+

, Na

+

, K

+

, NH

4

+

,

Ca

2+

, Sr

2+

, Ba

2+

S

2–

(sulfide)

Li

+

, Na

+

, K

+

, NH

4

+

,

Ca

2+

, Sr

2+

, Ba

2+

Solubility Rule II

Compounds that are Generally Insoluble

Slide27

27

How to predict the solubility of an ionic compound using the previous table?

Knowing how to use that table ALONE is generally sufficient to predict the solubility of ionic compound.

Rule of Thumb: if the ionic compound of interest does NOT contain any of the listed ions, it is INSOLUBLE! Example: Ca3(PO4)2if the ionic compound of interest contains BOTH the listed anion AND the cation as EXCEPTION, it is INSOLUBLE. Example: Hg2I2

Slide28

28

Predict an Ionic Compound’s Solubility in Water: HgSO

4

1. Check the cation: Is it Li+, Na+, K+, or NH4+? If YES  the compound will be soluble in waterregardless of the anion!If NO  follow the rule for the anion (Table 7.2)2. if a rule says the compounds are mostly soluble, then the exceptions are insoluble3. but if a rule says the compounds are mostly insoluble, then the exceptions are soluble

note: slightly soluble 

insoluble

Slide29

29

Practice:

Are they Soluble

in Water?

FeCl

3

Pb

(

C2H3O

2)

2BaSO4 (NH4)3PO4Generally SolubleExceptions

Li

+

, Na

+

, K

+

, NH

4

+

;

H

+

none

NO

3

, C

2

H

3

O

2

, ClO

4

None

Cl

, Br

, I

CI

S

MI

LE

SO

4

2–

Ag+, Ca

2+

, Sr2+, Ba2+, Pb2+

Slide30

30

Insoluble Ionic Compounds do not Dissociate into Ions

Insoluble Ionic compounds do not dissolve in water because the

Coulombic force among the ions is too strong for water molecules to break down the compound. Therefore they do not dissociate into ionsBaSO4(s)  Ba2+(aq) + SO42-(aq)

Slide31

31

Precipitation Reactions

When two soluble ionic compounds in aqueous solution mix, ion exchange will take place

AB + CD  AC + DB if one of the products is insoluble

in water, it will come out of solution as a precipitate

Slide32

32

Precipitation Reactions

The “Yellow Tornado”:

http://www.youtube.com/watch?v=RE-dFN7U91M&feature=related

Pb(NO

3

)

2

(aq) + 2 KI(aq)

 2 KNO3(aq) + PbI2(s)

Slide33

33

No Precipitate Formation =

No Reaction

KI(aq) + NaCl(aq)

KCl(aq) + NaI(aq)

all ions still present (all products are soluble),

no reaction

Slide34

34

Example: Write balanced equation between aqueous solution of sodium carbonate and aqueous solution of copper(II) chloride. Predict if precipitation forms.

Write the formulas of the reactants

Determine the ions present for each reactantExchange the IonsWrite the formulas of the productscross charges and reduceBalance the EquationDetermine the solubility of each productAdd “(s)” after the insoluble products and “(aq)” after the soluble products

Slide35

35

Predict if a reaction

will form

precipitateBaBr2 + Na2SO4  BaSO4 + NaBr

(NH4

)

3

PO

4

+ Ca(NO3

)

2  Ca3(PO4)2 + NH4NO32 NaOH + CuSO4

 Cu

(OH)

2

+ Na

2

SO

4

Generally Soluble

Exceptions

Li

+

, Na

+

, K

+

, NH

4

+

;

H

+

none

NO

3

, C

2

H

3

O

2

, ClO

4

None

Cl

, Br

, I

–CISMILE

SO

42–

Ag+, Ca2+, Sr2+, Ba2+, Pb2+

Slide36

36

Acid-Base Reactions

Also as

Neutralization reactions : the Acid and Base neutralize each other’s propertiesH+ from the Acid + OH- from the base  WaterCation from the base + Anion from the acid  salt (spectator ions)Acid + Base Salt + Water2 HNO3

(aq) + Ca(OH)2(aq)

Ca(NO

3

)

2(aq) + 2 H2O(l

)

Slide37

37

Example:- Write and Balance equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

Write the formulas of the reactants

Determine the ions present for each reactantExchange the ions, H+ combines with OH- to make H2O(l). Tip: write water as HOHWrite the formulas of the productsBalance the Equation (may be quickly balanced by matching the numbers of H and OH to make HOH)Determine the solubility of the saltWrite an (s) after the insoluble products and a (aq) after the soluble products. Water exists as liquid, so (l) for water.

Slide38

38

Gas-Evolving Reactions

Some reactions form a gas directly

From the ion exchangeK2S(aq) + H2SO4(aq)  K2SO4(aq

) + H2

S(g)

Other reactions form a gas by the decomposition of one of the products into a gas and water

Step 1: Na

2

CO3

(aq

) + H2SO4(aq)  Na2SO4(aq) + H2CO3(aq)Step 2: H2CO3

H

2

O(

l

) +

CO

2

(g)

Overall reaction:

Na

2

CO

3

(

aq

) + H

2

SO

4

(

aq

)

Na

2

SO

4

(

aq

) + H

2

O(

l

)

+ CO2(g)

Slide39

39

Compounds that Undergo

Gas Evolving Reactions

ReactantType

Reacting

With

Ion Exchange

Product

Decompose?

Gas

Formed

Example

metal

n

S,

metal HS

acid

H

2

S

no

H

2

S

K

2

S(aq) + 2HCl(aq)

2KCl(aq) + H

2

S(g)

metal

n

CO

3

,

metal HCO

3

acid

H

2

CO

3

yes

CO

2

K

2

CO

3

(aq) + 2HCl(aq)

2KCl(aq) + CO

2

(g) + H

2

O(

l

)metalnSO3

metal

HSO

3

acid

H2

SO3yes

SO

2K2SO3(aq) + 2HCl(aq)

2KCl(aq) + SO2(g) + H2O(l)

(NH

4)nanionbase

NH4OHyes

NH3KOH(aq) + NH

4

Cl(aq)

KCl(aq) + NH3(g) + H2O(l)

Slide40

40

Example:

Write and Balance equation between

an aqueous solution of sodium sulfite and an aqueous solution of nitric acid. Predict if precipitate or gas will form.Write the formulas of the reactantsDetermine the ions present when each reactant dissociatesExchange the IonsWrite the formulas of the productsCheck to see either product H2S, or if either product decomposes into gas (H2CO3, H2SO3, NH4OH). Balance the Equation

Determine the solubility of other product

Write “(s)”, or “(aq)”, or “(l) for water, or “(g)” for each product if appropriate

Slide41

41

Practice: Complete and Balance the following double-displacement Reactions; Predict whether the following reactions will form precipitate, gas, or neutralization (hint: predict the solubility of each compound)

HNO

3 + Al(OH)3 HCl + (NH4)2CO

3 

BaCl

2

+ (NH

4

)

2

CO3 

Slide42

42

Beyond Double Displacement Rxns

Precipitation

, Acid-Base, and Gas-evolving reactions all involved exchanging the ions in the solutionOxidation-Reduction reactions : reactions involve transferring electrons from one atom to another –also known as redox reactionsmany of these reactions are not done by dissolving the reactants in waterExamples: Reaction between elements, Single Displacement Reaction, Combustion Reaction

Slide43

43

Reactions of Metals with Nonmetals

(Oxidation-Reduction)

metals react with nonmetals to form ionic compoundsionic compounds are solids at room temperaturethe metal loses electrons and becomes a cationthe metal undergoes oxidation: Na  Na+ + e- the nonmetal gains electrons and becomes an anionthe nonmetal undergoes reduction: Cl

2

+ 2e

-

2 Cl

-

Overall Reaction: 2 Na(s) + Cl

2

(g)  2NaCl(s)

Slide44

Single-Replacement Reactions

Aka

Single-Displacement Reaction: A reaction in which a more active element displaces another less active element in a compound. A + BC  AB + CWhen iron bar placed in copper(II) sulfate solution: Iron is corroded, copper metal appears, blue color (Cu2+ ion) fades.Fe(s) + CuSO

4(aq) → FeSO4(aq) + Cu(s)Here ______ is more active than ____.

Slide45

Aqueous Acid Displacements

Metals that precede (H) in the activity series react with acids, and those that follow (H) do not react with acids.

More active metals react with acid to produce hydrogen gas and an ionic compound. Fe(s) + 2 HCl(aq) → FeCl2(aq) + H2(g)Metals less active than (H) show no reaction. Au(s) + H2SO4(aq) → NR

Slide46

Active Metals and Water

A few metals are active enough to react directly with water. These are called

active metals.They react with water to produce a metal hydroxide and hydrogen gas.2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)Ca(s) + 2 H2

O(l) → Ca(OH)2(aq) + H2(g)

Slide47

47

Combustion Reactions

Reactions in which O

2(g) is a reactant are called Combustion ReactionsCombustion reactions release lots of energyCombustion reactions are a subclass of Oxidation-Reduction reactions

2 C

8

H

18

(g) + 25 O

2

(g)

 16 CO2(g) + 18 H2O(g)

Slide48

48

Tro's Introductory Chemistry, Chapter 7

Combustion Products

to predict the products of a combustion reaction, combine each element in the other reactant with oxygen

Reactant

Combustion Product

contains C

CO

2

(g)

contains H

H

2

O(g)

contains S

SO

2

(g)

contains N

NO(g) or NO

2

(g)

contains metal

M

2

O

n

(s)

Slide49

49

Tro's Introductory Chemistry, Chapter 7

Combination Reactions

also known as

Composition or Synthesis

reactions

Two (or more) reactants combine together to make

one product

simpler substances combining together

2 CO + O2

® 2 CO

2CaO + H2O ® Ca(OH)2 2H2 + O2 ® 2H2O

Slide50

50

Tro's Introductory Chemistry, Chapter 7

Decomposition Reactions

ONE large molecule is broken apart into smaller molecules or its elements

caused by addition of energy into the molecule

From one reactant

,

make 2 or more products

Slide51

51

Practice: Write and Balance Word Equations

iron(III) chloride + copper metal

 iron(II) chloride + copper(II) chloridenitrogen gas + magnesium metal  magnesium nitridezinc phosphate + hydrochloric acid  phosphoric acid + zinc

chloride

Slide52

52

Determine if Each of the Following is Soluble in Water

KOH

Soluble, because the cation is K

+

AgBr

Insoluble, even though most compounds with Br

-

are soluble, this is an exception

CaCl2 Soluble, most compounds with Cl-

are solublePb(NO

3)2 Soluble, because the anion is NO3-SrSO4 Insoluble, even though most compounds with SO42- are soluble, this is an exception

Slide53

53

Example: When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms

Write the formulas of the reactants

Na2CO3(aq) + CuCl2(aq) Determine the ions present when each reactant dissociates(Na+ + CO32-) + (Cu2+ + Cl

-) 

Exchange the Ions

(Na

+

+ CO

32-) + (Cu

2+ + Cl

-)  (Na+ + Cl-) + (Cu2+ + CO32-)

Slide54

54

Write the formulas of the products

cross charges and reduce

Na2CO3(aq) + CuCl2(aq)  NaCl + CuCO3Balance the EquationNa2CO3(aq) + CuCl2(aq)

 2 NaCl

+ CuCO

3

Example: When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms

Slide55

55

Determine the solubility of each product

NaCl is soluble

CuCO3 is insolubleWrite an (s) after the insoluble products and a (aq) after the soluble productsNa2CO3(aq) + CuCl2(aq)  2 NaCl(aq) + CuCO3(s)

Example - When an aqueous solution of sodium carbonate is added to an aqueous solution of copper(II) chloride, a white solid forms

Slide56

56

Example:- Write and Balance equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

Write the formulas of the reactants

HNO3(aq) + Ca(OH)2(aq) Determine the ions present when each reactant dissociates(H+ + NO3-) + (Ca2+ + OH-

) 

Exchange the ions, H

+

combines with OH

-

to make H2O(l). Tip: write water as HOH(H

+ + NO

3-) + (Ca2+ + OH-)  (Ca2+ + NO3-) + HOH(l)

Slide57

57

Write the formulas of the products

cross charges and reduce

HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2 + HOH(l)Balance the Equationmay be quickly balanced by matching the numbers of H and OH to make HOHcoefficient of the salt is always 12 HNO3(aq) + Ca(OH)

2(aq)

Ca(NO

3

)

2 + 2 HOH(l)

Example: Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

Slide58

58

Determine the solubility of the salt

Ca(NO

3)2 is solubleWrite an (s) after the insoluble products and a (aq) after the soluble products2 HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2(aq) + 2 H2

O(l)

Example 7.11 - Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide

Slide59

59

Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves

Write the formulas of the reactants

Na2SO3(aq) + HNO3(aq) Determine the ions present when each reactant dissociates(Na+ + SO32-) + (H+ + NO

3-)

Exchange the Ions

(Na

+

+ SO3

-) + (H

+ + NO3-)  (Na+ + NO3-) + (H+ + SO32-)

Slide60

60

Write the formulas of the products

cross charges and reduce

Na2SO3(aq) + HNO3(aq)  NaNO3 + H2SO3Check to see either product H2S - NoCheck to see of either product decomposes – Yes

H2SO

3

decomposes into SO

2

(g) + H

2O(l)

Na2

SO3(aq) + HNO3(aq)  NaNO3 + SO2(g) + H2O(l)Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves

Slide61

61

Balance the Equation

Na

2SO3(aq) + 2 HNO3(aq)  2 NaNO3 + SO2(g) + H2O(l)Determine the solubility of other productNaNO3 is soluble

Write an (s) after the insoluble products and a (aq) after the soluble products

Na

2

SO

3

(aq) + 2 HNO3(aq)  2 NaNO

3(aq)

+ SO2(g) + H2O(l)Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves

Slide62

62

Practice:

Complete and Balance the following Word equations

copper(II) nitrate + sodium carbonatesilver acetate + ammonium chloridepotassium carbonate + phosphoric acidbarium hydroxide + sulfuric acid

Slide63

63

Practice:

Complete and Balance the following Word equations

copper(II) nitrate + sodium carbonatesilver acetate + ammonium chloridepotassium carbonate + phosphoric acidbarium hydroxide + sulfuric acid Cu(NO3)2(aq) + Na2CO3(aq)  2

NaNO3(aq) + CuCO

3

(s)

AgC

2

H3O

2(aq) + NH

4Cl(aq)  AgCl(s) + NH4C2H3O2(aq) 3K2CO3(aq) + 2H3PO4(aq)  2K

3

PO

4

(aq) + 3H

2

O(l) + 3CO

2

(g)

Ba(OH)

2

(aq) + H

2

SO

4

(aq)

 BaS

O

4

(s) + 2 H

2

O(l)