1. Chapter 11 “Chemical Reactions”

2. A. List as many examples of chemical reactions as you can.
Tuesday
A. List as many examples of chemical reactions as you can.
B. In your own words, try to describe what a chemical reaction is.

3. Law of conservation of… Matter Mass 3 classes of elements?
Before we start Chapter 11… you guys have a lot of the knowledge already
Law of conservation of…
Matter
Mass
3 classes of elements?
3 states of matter?
3 types of compounds?

4. Section 11.1 Describing Chemical Reactions
OBJECTIVES:
Describe how to create a
word equation.
skeleton equation
Balanced chemical equation

5. Section 11.1 Describing Chemical Reactions
Vocabulary:
Chemical reaction
Skeleton equation
Catalyst
Coefficients
Balanced equations

6. All chemical reactions…
have two parts:
Reactants = the substances you start with
Products = the substances you end up with
The reactants will turn into the products.
Reactants ® Products

7. - Page 321
Products
Reactants

8. In a chemical reaction
Atoms aren’t created or destroyed (according to the Law of Conservation of Matter)
A reaction can be described several ways:
#1. In a sentence every item is a word: Copper reacts with chlorine to form copper (II) chloride.
#2. In a word equation some symbols are used:
Copper + chlorine ® copper (II) chloride

9. Symbols in equations? – Text page 323
the arrow (→) separates the reactants from the products (arrow points to products)
Read as: “reacts to form” or yields
The plus sign = “and”
(s) = solid: Fe(s)
(g) = gas: CO2(g)
(l) = liquid: H2O(l)

10. Symbols used in equations
(aq) after the formula = dissolved in water, an aqueous solution: NaCl(aq) is a salt water solution
(more in 11.3)

11. Symbols used in equations
double arrow indicates a reversible reaction (more later)
shows that heat is supplied to the reaction
is used to indicate a catalyst is supplied (in this case, platinum is the catalyst)

12. Enzymes are biological or protein catalysts in your body.
What is a catalyst?
A substance that speeds up a reaction, without being changed or used up by the reaction.
Enzymes are biological or protein catalysts in your body.

13. #3. The Skeleton Equation
Uses formulas and symbols to describe a reaction
but doesn’t indicate how many; this means they are NOT balanced
All chemical equations are a description of the reaction.

14. Now, read these equations:
Fe(s) + O2(g) ® Fe2O3(s)
Cu(s) + AgNO3(aq) ® Ag(s) + Cu(NO3)2(aq)
NO2(g) N2(g) + O2(g)

15. Write a skeleton equation for:
Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gas.
Nitric acid dissolved in water reacts with solid sodium carbonate to form liquid water and carbon dioxide gas and sodium nitrate dissolved in water.

16. Wednesday – 3.9.11 Tonight’s HW: P. 347 #36-43
BR: Write the following as chemical equations
1. Sulfur dioxide gas mixed with oxygen gas yields Sulfur trioxide gas
2. Hydrogen gas mixed with oxygen gas produces liquid water
3. Solid phosphorous added to oxygen gas yields tetraphosphorous decoxide
Tonight’s HW:
P. 347 #36-43
A really good summary of 11.1

17. #4. Balanced Chemical Equations
Atoms can’t be created or destroyed in an ordinary reaction:
All the atoms we start with we must end up with (meaning: balanced!)
A balanced equation has the same number of each element on both sides of the equation.

18. Rules for balancing:
Assemble the correct formulas for all the reactants and products, using “+” and “→”
Count the # of atoms of each type appearing on both sides
Balance the elements one at a time by adding coefficients (the numbers in front) where you need more - save balancing the H and O until LAST!
(save O until the very last)
Double-Check to make sure it is balanced.

19. Never
Never change a subscript to balance an equation (You can only change coefficients)
If you change the subscript (formula) you are describing a different chemical.
H2O is a different compound than H2O2
Never put a coefficient in the middle of a formula; they must go only in the front
2NaCl is okay, but Na2Cl is not.

20. Practice Balancing Examples
_AgNO3 + _Cu ® _Cu(NO3)2 + _Ag
_Mg + _N2 ® _Mg3N2
_P + _O2 ® _P4O10
_Na + _H2O ® _H2 + _NaOH
_CH4 + _O2 ® _CO2 + _H2O 2 2 3 4 5 2 2 2 2 2

21. Practice Balancing Examples
_SO2 + _O2  _SO3
_Fe2O3 + _H2  _Fe + _H2O
_P + _O2  _P4O10
_Al + _N2  _AlN
_PbO2  _PbO + _O2

22. Thursday 3.10.11 BR: Balance the following equations:
_P + _O2  _P4O10 _KClO3  _KCl + _O2
_C3H8 + _O2  _CO2 + _H2O
And this one if you can…: _HCl +_CaCO3  _H2O + _CO2 + _CaCl2

23. Agenda Bellringer (HW check) Review of 11.1 Homework (11.1 WS)
11.2 reading notes
Due at end of class (11.1 notes w/summary)
Exit slip

24. #36 Identify the reactants and products in each chemical rxn
Hydrogen gas and sodium hydroxide are formed when sodium is dropped into water
In photosynthesis, carbon dioxide and water react to form oxygen gas and glucose

25. #37
How did John Dalton explain a chemical reaction using his atomic theory?

26. #38 What is the function of an arrow () in a chemical equation?
A plus sign? (+)

27. #39
Write sentences that completely describe each of the chemical reactions shown in these skeleton equations.
NH3 (g) + O2(g)  NO(g) + H2O (g)
H2SO4(aq) + BaCl2 (aq)  BaSO4 (s) + HCl (aq)
N2O3(g) + H2O(l)  HNO2 (aq)

28. 40
What is the purpose of a catalyst?

29. 41
Balance equations for each item. The formula for each product is given:
A basketball team:
Center + Forward +Guard  team
C + F + G  CF2G2
A tricycle
Frame + wheel + seat + pedal  trike
F + W + S + P  FW3SP2

30. 42
The equation for the formation of water from its elements, H2(g) + O2(g)  H2O(l), can be ‘balanced’ by changing the formula of the product to H2O2,
EXPLAIN WHY THIS IS INCORRECT

31. 43 BALANCE THE FOLLOWING EQUATIONS. A. _PbO2  _PbO + _O2
B. _Fe(OH)3  _Fe2O _H2O
C. _(NH4)2CO3  _NH3 + _H2O + _CO2
D. _NaCl + _H2SO4  _Na2SO4 + _HCl

32. Writing Section 11.1 Summary: All of the following should be included:
OBJECTIVES:
Describe how to create a
word equation.
skeleton equation
Balanced chemical equation
Vocabulary:
Chemical reaction
Skeleton equation
Catalyst
Coefficients
Balanced equations

33. Homework (Due Monday)
(11.1 WS)
11.2 reading notes

34. Friday, 3.11.11 What’s due on Monday?
BR: Balance the following 5 equations (hint  all coefficients will be 2):
_Mg + _O2  _MgO
_HgO  _Hg + _O2
_K + _H2O  _KOH + H2
_K2CO3 + _BaCl2  _KCl + _BaCO3
_CH4 + _O2  _CO2 + _H2O
What’s due on Monday?
11.2 reading notes (no summary necessary)
Balancing WS #1
Balancing WS #2

35. BR 2Mg + _O2  2MgO 2HgO  2Hg + _O2 _K + _H2O  _KOH + H2
_K2CO3 + _BaCl2  _KCl + _BaCO3
_CH4 + _O2  _CO2 + _H2O

36. BR 2Mg + _O2  2MgO 2HgO  2Hg + _O2 2K + 2H2O  2KOH + H2
_K2CO3 + _BaCl2  _KCl + _BaCO3
_CH4 + _O2  _CO2 + _H2O

37. BR 2Mg + _O2  2MgO 2HgO  2Hg + _O2 2K + 2H2O  2KOH + H2
_K2CO3 + _BaCl2  2KCl + _BaCO3
_CH4 + _O2  _CO2 + _H2O

38. BR 2Mg + _O2  2MgO 2HgO  2Hg + _O2 2K + 2H2O  2KOH + H2
_K2CO3 + _BaCl2  2KCl + _BaCO3
_CH4 + 2O2  _CO2 + 2H2O

39. Rules for balancing:
Assemble the correct formulas for all the reactants and products, using “+” and “→”
Count the # of atoms of each type appearing on both sides
Balance the elements one at a time by adding coefficients (the numbers in front) where you need more - save balancing the H and O until LAST!
(save O until the very last)
Double-Check to make sure it is balanced.

40. Never
Never change a subscript to balance an equation (You can only change coefficients)
If you change the subscript (formula) you are describing a different chemical.
H2O is a different compound than H2O2
Never put a coefficient in the middle of a formula; they must go only in the front
2NaCl is okay, but Na2Cl is not.

41. Section 11.2 Types of Chemical Reactions
OBJECTIVES:
Describe 5 types of reactions.
Predict products for combination & decomposition reactions.

42. Types of Reactions
There are millions of reactions organized into several categories.
We will learn:
a) 5 major types.
b) how to predict the products based on their reactants

43. #1 - Combination Reactions
Combine = put together
Also called “synthesis” rxns
Ca + O2 ® CaO
SO3 + H2O ® H2SO4
We can predict the products, easily if the reactants are two elements.
Mg + N2 ® _______
Mg3N2 (symbols, charges, cross)

44. Complete and balance:
Ca + Cl2 ®
Al + O2 ®
1: Write correct formulas – you can change the subscripts ONLY now
2: Balance by changing just the coefficients only

45. #2 - Decomposition Reactions
decompose = fall apart
1 reactant  2 or more elements or compounds.
NaCl Na + Cl2
CaCO CaO + CO2
Note that energy (heat, sunlight, electricity, etc.) is usually required

46. #2 - Decomposition Reactions
We can predict products if it is a binary compound (which means it is made up of only two elements)
It breaks apart into the elements:
H2O
HgO

47. #2 - Decomposition Reactions
If the compound has more than two elements you must be given one of the products
The other product will be from the missing pieces
NiCO CO2 + ___
H2CO3(aq) ® CO2 + ___
heat

48. #3 - Single Replacement Reactions
One element replaces another
Reactants must be an element and a compound.
Products will be a different element and a different compound.
Na + KCl ® K + NaCl
F2 + LiCl ® LiF + Cl2
(Cations switched)
(Anions switched)

49. #3 Single Replacement Reactions
Metals will replace other metals (and they can also replace hydrogen)
K + AlN ®
Zn + HCl ®
Think of water as: HOH
Metals replace the first H, and then combines with the hydroxide (OH).
Na + HOH ®

50. #3 Single Replacement Reactions Practice:
Fe + CuSO4 ®
Pb + KCl ®

51. #4 - Double Replacement Reactions
Two things replace each other.
Reactants must be two ionic compounds, in aqueous solution
NaOH + FeCl3 ®
The positive ions change place.
NaOH + FeCl3 ® Fe+3 OH- + Na+1 Cl-1
= NaOH + FeCl3 ® Fe(OH)3 + NaCl

52. Complete and balance:
assume all of the following reactions actually take place:
CaCl2 + NaOH ®
KOH + Fe(NO3)3 ®

53. 3.15.11 BR: Identify only WHAT TYPE of equation for the following:
H2 + O2 ®
H2O ®
Zn + H2SO4 ®
HgO ®
KBr + Cl2 ®
AgNO3 + NaCl ®
Mg(OH)2 + H2SO3 ®

54. IMPORTANT SLIDE How to determine type of reaction
Look at the reactants: (E = element and C = Compound)
E + E = Combination
C = Decomposition
E + C = Single replacement
C + C = Double replacement

55. #5 – Combustion Reactions
Combustion means “add oxygen”
Normally, a compound made of only C, H, (and maybe O) reacts with oxygen – usually called “burning”
If the combustion is complete, the products will be CO2 and H2O.
If the combustion is incomplete, the products will be CO (or possibly just C) and H2O.

56. Combustion Reaction Examples:
C4H10 + O2 ® CO2 + H2O (complete)
C4H10 + O2 ® CO + H2O (incomplete)
C6H12O6 + O2 ® CO2 + H2O (complete)
C8H8 + O2 ® CO + H2O (incomplete)

57. A + B → AB AB → A + B CxHy + O2 → CO2 + H2O AB + C → AC + B
Type of Reaction
Definition
 Equation
Combination
Decomposition
Single Replacement
Double Replacement
Combustion
When oxygen reacts with a element or compound to produce H2O and CO2 (complete) or CO (incomplete)
CxHy + O2 → CO2 + H2O
Two or more elements or compounds combine to make a more complex substance
A + B → AB
AB → A + B
Compounds break down
into simpler substances
Occurs when one element replaces another one in a compound
AB + C → AC + B
Occurs when different atoms in two different compounds trade places
AB + CD → AC + BD
A = Red B = Blue C = Green D = Yellow

58. SUMMARY: An equation... Describes a reaction
Must be balanced in order to follow the Law of Conservation of Mass
Can only be balanced by changing the coefficients.
Has special symbols to indicate the physical state, if a catalyst or energy is required, etc.

60. HW
P. 339 All questions
11.2 summary

61. Section 11.3 Reactions in Aqueous Solution
OBJECTIVES:
Describe the information found in a net ionic equation.
Predict the formation of a precipitate in a double replacement reaction.

62. Net Ionic Equations
Many reactions occur in water- that is, in aqueous solution
When dissolved in water, many ionic compounds “dissociate”, or separate, into cations and anions
Now we are ready to write an ionic equation

63. Net Ionic Equations
Example (needs to be a double replacement reaction)
AgNO3 + NaCl  AgCl + NaNO3
1. this is the full balanced equation
2. next, write it as an ionic equation by splitting the compounds into their ions:
Ag1+ + NO31- + Na1+ + Cl1- 
AgCl + Na1+ + NO31-
Note that the AgCl did not ionize, because it is a “precipitate”

64. Net Ionic Equations
3. simplify by crossing out ions not directly involved (called spectator ions)
Ag1+ + Cl1-  AgCl
This is called the net ionic equation
Let’s talk about precipitates before we do some other examples

65. Predicting the Precipitate
Insoluble salt = a precipitate [note Figure 11.11, p.342 (AgCl)]
General solubility rules are found:
Table 11.3, p. 344 in textbook
Reference section - page R54 (back of textbook)
Your periodic table handout

66. Let’s do some examples together of net ionic equations, starting with these reactants:
BaCl2 + AgNO3 →
NaCl + Ba(NO3)2 →
End of Chapter 11