1. Chemical Reactions Balance Equation Double-displacement Reaction:
Precipitation
acid-base neutralization
gas-evolving
Single-displacement Reaction

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 2

3. Chemical Reactions Reactants  Products
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 3

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 Product
All 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 4

5. Components in Chemical Equations: 2Mg(s) + O2(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) 5

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 = mechanical
elec = electrical 6

7. Combustion of Methane: Balanced!
To obey the Law of Conservation of Mass, the equation must be balanced
CH4(g) + 2 O2(g) ® CO2(g) + 2 H2O(g) O C + O H + O + H C +
1 C H O 7

8. Balance Table CH4(g) + 2 O2(g) ® CO2(g) + 2 H2O(g)
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  1
4  H  4
4  O  2 + 2 8

9. How to Write & Balance Chemical Equation
__CH4O(g) + __O2(g) ® __CO2(g) + __H2O(g)
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. 9

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 formula
Find the Least Common Multiple of the number of atoms on each side. 10

11. Example: Balance as Ions
Fe(CN)3(s) + H2SO4(aq) ® Fe2(SO4)3(aq) + HCN(aq)
____ and ____ are groups 11

12. Example: Balance equation
C8H18 + O2 ® CO2 + H2O 12

13. Practice: Balancing Equations
C12H22O O2  CO2 + H2 O
(NH4)3PO4 + Ca(NO2)2  Ca3(PO4)2 + NH4NO2

14. Classifying Reactions
A. based on the process that happens (we observes)
precipitation, neutralization, formation of a gas, or transfer of electrons

15. Classifying Reactions
B. by what the atoms and/or ions do (at molecular/atomic level)
Type of Reaction
General Equation
Synthesis
A + B  AB
Decomposition
AB  A + B
Displacement
A + BC  AC + B
Double Displacement
AB + CD  AD + CB

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 16

17. Double Displacement Reactions
Exchange ionic partners: AB + CD  AD + CB
Example: 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)

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 18

19. Dissociation of Ionic Compound
Dissociation: 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 19

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
SO4
SO42- Cu
Cu2+ 20

21. Polyatomic Ionic Compounds
Ammonium sulfate  ammonium cations and sulfate anions
(NH4)2SO4(aq)  2 NH4+(aq) + SO42-(aq)
SO4
SO42-
NH4+
NH4+
NH4+
NH4+ 21

22. Practice: How Ionic Compounds Dissociate?
Ammonium phosphate
Cobalt(III) sulfate
Zinc bromide

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 water
a 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 water
though there is a very small amount dissolved, but not enough to be significant

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 24

25. Solubility Rule. Part I Compounds that are Generally Soluble in Water
Compounds Containing the following Ions are Generally Soluble
Exceptions
(insoluble when combined with ions on the left)
Li+, Na+, K+, NH4+;
H+ (most acids in this class)
none
NO3–, C2H3O2–, ClO4–
None
Cl–, Br–, I–
Cu+, Ag+, Hg22+, Pb2+ (CISMILE)
SO42–
Ag+, Ca2+, Sr2+, Ba2+, Pb2+

26. Solubility Rule II Compounds that are Generally Insoluble
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+, NH4+,
Ca2+, Sr2+, Ba2+
S2– (sulfide) 26

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)2
if the ionic compound of interest contains BOTH the listed anion AND the cation as EXCEPTION, it is INSOLUBLE. Example: Hg2I2

28. Predict an Ionic Compound’s Solubility in Water: HgSO4
1. Check the cation: Is it Li+, Na+, K+, or NH4+?
If YES  the compound will be soluble in water
regardless 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 insoluble
3. but if a rule says the compounds are mostly insoluble, then the exceptions are soluble
note: slightly soluble  insoluble

29. Practice: Are they Soluble in Water?
FeCl3
Pb(C2H3O2)2
BaSO4
(NH4)3PO4
Generally Soluble
Exceptions
Li+, Na+, K+, NH4+; H+
none
NO3–, C2H3O2–, ClO4–
None
Cl–, Br–, I–
CISMILE
SO42–
Ag+, Ca2+, Sr2+, Ba2+, Pb2+

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 ions
BaSO4(s)  Ba2+(aq) + SO42-(aq)

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

32. Precipitation Reactions
The “Yellow Tornado”:
Pb(NO3)2(aq) + 2 KI(aq)  2 KNO3(aq) + PbI2(s)

33. No Precipitate Formation = No Reaction
KI(aq) + NaCl(aq)  KCl(aq) + NaI(aq)
all ions still present (all products are soluble),
 no reaction

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 reactant
Exchange the Ions
Write the formulas of the products
cross charges and reduce
Balance the Equation
Determine the solubility of each product
Add “(s)” after the insoluble products and “(aq)” after the soluble products

35. Predict if a reaction will form precipitate
BaBr2 + Na2SO4  BaSO4 + NaBr
(NH4)3PO4 + Ca(NO3)2  Ca3(PO4)2 + NH4NO3
2 NaOH + CuSO4  Cu(OH)2 + Na2SO4
Generally Soluble
Exceptions
Li+, Na+, K+, NH4+; H+
none
NO3–, C2H3O2–, ClO4–
None
Cl–, Br–, I–
CISMILE
SO42–
Ag+, Ca2+, Sr2+, Ba2+, Pb2+

36. Acid + Base Salt + Water
Acid-Base Reactions
Also as Neutralization reactions : the Acid and Base neutralize each other’s properties
H+ from the Acid + OH- from the base  Water
Cation from the base + Anion from the acid  salt (spectator ions)
Acid + Base Salt + Water
2 HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2(aq) + 2 H2O(l)

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

38. Gas-Evolving Reactions
Some reactions form a gas directly
From the ion exchange
K2S(aq) + H2SO4(aq)  K2SO4(aq) + H2S(g)
Other reactions form a gas by the decomposition of one of the products into a gas and water
Step 1: Na2CO3(aq) + H2SO4(aq)  Na2SO4(aq) + H2CO3(aq)
Step 2: H2CO3  H2O(l) + CO2(g)
Overall reaction:
Na2CO3(aq) + H2SO4(aq)  Na2SO4(aq) + H2O(l) + CO2(g)

39. Compounds that Undergo Gas Evolving Reactions
Reactant
Type
Reacting
With
Ion Exchange
Product
Decompose?
Gas
Formed
Example
metalnS,
metal HS
acid
H2S no
K2S(aq) + 2HCl(aq) 
2KCl(aq) + H2S(g)
metalnCO3,
metal HCO3
H2CO3
yes
CO2
K2CO3(aq) + 2HCl(aq) 
2KCl(aq) + CO2(g) + H2O(l)
metalnSO3
metal HSO3
H2SO3
SO2
K2SO3(aq) + 2HCl(aq) 
2KCl(aq) + SO2(g) + H2O(l)
(NH4)nanion
base
NH4OH
NH3
KOH(aq) + NH4Cl(aq) 
KCl(aq) + NH3(g) + H2O(l)

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 reactants
Determine the ions present when each reactant dissociates
Exchange the Ions
Write the formulas of the products
Check 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

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)
HNO3 + Al(OH)3 
HCl + (NH4)2CO3 
BaCl2 + (NH4)2CO3 

42. Beyond Double Displacement Rxns
Precipitation, Acid-Base, and Gas-evolving reactions all involved exchanging the ions in the solution
Oxidation-Reduction reactions : reactions involve transferring electrons from one atom to another –
also known as redox reactions
many of these reactions are not done by dissolving the reactants in water
Examples: Reaction between elements, Single Displacement Reaction, Combustion Reaction

43. Reactions of Metals with Nonmetals (Oxidation-Reduction)
metals react with nonmetals to form ionic compounds
ionic compounds are solids at room temperature
the metal loses electrons and becomes a cation
the metal undergoes oxidation: Na  Na+ + e-
the nonmetal gains electrons and becomes an anion
the nonmetal undergoes reduction: Cl2+ 2e- 2 Cl-
Overall Reaction: 2 Na(s) + Cl2(g)  2NaCl(s)

44. 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 + C
When iron bar placed in copper(II) sulfate solution: Iron is corroded, copper metal appears, blue color (Cu2+ ion) fades.
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
Here ______ is more active than ____.

45. 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

46. 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 H2O(l) → Ca(OH)2(aq) + H2(g)

47. Combustion Reactions
Reactions in which O2(g) is a reactant are called Combustion Reactions
Combustion reactions release lots of energy
Combustion reactions are a subclass of Oxidation-Reduction reactions
2 C8H18(g) + 25 O2(g)  16 CO2(g) + 18 H2O(g)

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
CO2(g)
contains H
H2O(g)
contains S
SO2(g)
contains N
NO(g) or NO2(g)
contains metal
M2On(s)
Tro's Introductory Chemistry, Chapter 7

49. 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 CO2
CaO + H2O ® Ca(OH)2
2H2 + O2 ® 2H2O
Tro's Introductory Chemistry, Chapter 7

50. 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
Tro's Introductory Chemistry, Chapter 7

51. Practice: Write and Balance Word Equations
iron(III) chloride + copper metal  iron(II) chloride + copper(II) chloride
nitrogen gas + magnesium metal  magnesium nitride
zinc phosphate + hydrochloric acid  phosphoric acid + zinc chloride

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

53. Write the formulas of the reactants
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+ + CO32-) + (Cu2+ + Cl-)  (Na+ + Cl-) + (Cu2+ + CO32-)

54. Write the formulas of the products
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 products
cross charges and reduce
Na2CO3(aq) + CuCl2(aq)  NaCl + CuCO3
Balance the Equation
Na2CO3(aq) + CuCl2(aq)  2 NaCl + CuCO3

55. Na2CO3(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
Determine the solubility of each product
NaCl is soluble
CuCO3 is insoluble
Write an (s) after the insoluble products and a (aq) after the soluble products
Na2CO3(aq) + CuCl2(aq)  2 NaCl(aq) + CuCO3(s)

56. (H+ + NO3-) + (Ca2+ + OH-)  (Ca2+ + NO3-) + HOH(l)
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+ + NO3-) + (Ca2+ + OH-)  (Ca2+ + NO3-) + HOH(l)

57. Write the formulas of the products
Example: Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide
Write the formulas of the products
cross charges and reduce
HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2 + HOH(l)
Balance the Equation
may be quickly balanced by matching the numbers of H and OH to make HOH
coefficient of the salt is always 1
2 HNO3(aq) + Ca(OH)2(aq)  Ca(NO3) HOH(l)

58. Example Write the molecular equation for the reaction of aqueous nitric acid with aqueous calcium hydroxide
Determine the solubility of the salt
Ca(NO3)2 is soluble
Write an (s) after the insoluble products and a (aq) after the soluble products
2 HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2(aq) + 2 H2O(l)

59. (Na+ + SO3-) + (H+ + NO3-)  (Na+ + NO3-) + (H+ + SO32-)
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+ + NO3-) 
Exchange the Ions
(Na+ + SO3-) + (H+ + NO3-)  (Na+ + NO3-) + (H+ + SO32-)

60. 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 products
cross charges and reduce
Na2SO3(aq) + HNO3(aq)  NaNO3 + H2SO3
Check to see either product H2S - No
Check to see of either product decomposes – Yes
H2SO3 decomposes into SO2(g) + H2O(l)
Na2SO3(aq) + HNO3(aq)  NaNO3 + SO2(g) + H2O(l)

61. Example - When an aqueous solution of sodium sulfite is added to an aqueous solution of nitric acid, a gas evolves
Balance the Equation
Na2SO3(aq) + 2 HNO3(aq)  2 NaNO3 + SO2(g) + H2O(l)
Determine the solubility of other product
NaNO3 is soluble
Write an (s) after the insoluble products and a (aq) after the soluble products
Na2SO3(aq) + 2 HNO3(aq)  2 NaNO3(aq) + SO2(g) + H2O(l)

62. Practice: Complete and Balance the following Word equations
copper(II) nitrate + sodium carbonate
silver acetate + ammonium chloride
potassium carbonate + phosphoric acid
barium hydroxide + sulfuric acid

63. Practice: Complete and Balance the following Word equations
copper(II) nitrate + sodium carbonate
silver acetate + ammonium chloride
potassium carbonate + phosphoric acid
barium hydroxide + sulfuric acid
Cu(NO3)2(aq) + Na2CO3(aq)
 2 NaNO3(aq) + CuCO3(s)
AgC2H3O2(aq) + NH4Cl(aq)
 AgCl(s) + NH4C2H3O2(aq)
3K2CO3(aq) + 2H3PO4(aq)
 2K3PO4(aq) + 3H2O(l) + 3CO2(g)
Ba(OH)2(aq) + H2SO4(aq)
 BaSO4(s) + 2 H2O(l)