1. Matter and Change 2.2.1 Describing Chemical Reactions Unit 2 Section 2
2.2.2 Types of Chemical Reactions
2.2.3 Reactions in Aqueous Solution

2. 2.2.1 Chemical Reactions Examples of Chemical Reactions
Rusting of iron
Burning (combustion) of wood
Cooking
Vinegar + Baking soda ->
Photosynthesis
6CO2 + 6H2O + Energy --> C6H12O6 + 6O2

3. Chemical reactions are like sentences.
Symbols  Formula  Equations 
elements
compounds
chemical reactions
Put letters together to make words. Put words together to make sentences.

4. Chemical reaction
a reaction that occurs when the atoms of one of more substances are rearranged to form different substances
a chemical change
Evidence of a chemical reaction
- Temperature change
- Color change
- Odor produced
- Formation of bubbles
- Appearance of a solid

5. Chemical Equations 2H2(g) + O2(g) 2H2O (l)
Reactants: elements or compounds to the left of the arrow that combine together in a chemical reaction
Products: elements or compounds to the right of the arrow that are produced in a chemical reaction
Coefficient: whole number before a chemical formula
Subscript: small lowered number after a chemical symbol
+ : represents “and”
: direction reaction progresses, yields or produces

6. C(s) O2(g) CO2 (g)
physical states of reactants and products are indicated by:
(s) = solid:    C(s)
(g) = gas:    CO2(g) 
(l) = liquid:    H2O(l)
(aq) = aqueous, dissolved in water,
NaCl(aq) is a salt water solution
(cr) = crystalline
= precipitate forms

7. Chemical Equations CH4(g) + 2 O2(g) 2 H2O (l) + CO2(g)
Identify the following and label
Reactants:
Products:
Coefficient:
Subscript:
+ define
define

8. Covalent Bonding GEN-U-INE
A molecule is a neutral group of atoms joined together by covalent bonds.
Diatomic molecules – molecules made up of the same element
Examples: O2 , H2 , N2, F2 , Cl2 , Br2 , I2
GEN-U-INE

9. Word and Formula Equations
A skeleton equation represents the reactants and products of a chemical reaction by their formulas.
Example: Na(s) + Cl2(g) NaCl(s)

10. Balancing Chemical Equations
balanced chemical equation – shows that each side of the equation has the same number of atoms of each element and mass is conserved
Na(s) Cl2(g) NaCl(s)
Law of conservation - in a chemical reaction matter is neither created nor destroyed
Chemical equations must be balanced using coefficients 2 2

11. Balancing Equations 2 2 2 2 2 2 3 3 4 5 2 ____ K + ____ Cl2  ____ KCl
____ Ag + ____ O2  ____ Ag2O
____ LiBr + ____ I2  ____ LiI + ____ Br2
____ Na + ____ AlF3  ____ NaF + ____ Al
____ P + ____ O2  ____ P2O5 2 2 2 2 3 3 4 5 2

12. Balance the following equations
Mg + O2 ----> MgO KClO3 ----> KCl + O2 Na + MgCl2 ----> NaCl + Mg

13. Word and Formula Equations
A word equation is an equation represented by words.
Example: solid sodium plus chlorine gas reacts to produce sodium chloride

14. Steps for Translating Word Equations
1) Scan for DIATOMICS and label 2) Write skeleton equation: assemble the correct formulas 3) Count the number of atoms of elements in reactants 4) Count the number of atoms of elements in products 5) Balance the elements one at a time by adding coefficients in front of a formula to make number of atoms equal on both sides of equation 6) Check to make sure equation is balanced and coefficients are in lowest possible ratio

15. Sample Word Equations – Balancing Equations
Scan for DIATOMICS!
Word Equation 1
Hydrogen plus oxygen yields water
Skeleton Equation
Balanced Equation

16. Sample problems – Balancing Equations
Example 2
Calcium bromide plus fluorine yields calcium fluoride and bromine
Skeleton / Balanced Equation

17. Example 3
Water and iron react to form iron III oxide and hydrogen
Propane (C3H8) burns in oxygen to form carbon dioxide and water
Example 4

18. Do-Now
Identify and write the polyatomic ion using your ion chart. Include charge!
sulfate – hydroxide –
nitrate – phosphate –
Write the formulas for the following compounds. Must show charge and crisscross!
Potassium oxide 3. Iron (III) hydroxide
Calcium chloride 4. Barium sulfate

19. Chemical Reactions 11.3 Reactions in Aqueous Solution
Chapter 11
Chemical Reactions
11.1 Describing Chemical Reactions
11.2 Types of Chemical Reactions
11.3 Reactions in Aqueous Solution
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20. What happens to the wax when you burn a candle?
CHEMISTRY & YOU
What happens to the wax when you burn a candle?
When you burn a candle, a chemical reaction called combustion takes place.
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21. Classifying Reactions
What are the five general types of reactions?
Synthesis (or combination)
Decomposition
Singe-replacement
Double-replacement
Combustion
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22. 1. Synthesis Reactions (Combination)
Two (or more) reactants combine to form one product
general form: A B AB
specific types:
2 elements: Fe S Fe+2S-2
2 compounds: Ca+2O H2O Ca+2(OH)-12
1 element, 1 compound: SO O SO3

23. 2. Decomposition Reactions
one reactant breaks down into two or more products
general form: AB A B
Examples: Na+1N Na N2
Ca+2(CO3) Ca+2O CO2
*decomposition reactions require energy
heat >
electricity --->
catalyst > 3

24. Classify each reaction as Synthesis or Decomposition
_________________ 2 Na + Cl2 ---> 2NaCl
_________________ CaCO > CaO + CO2
_________________ H2O > 2H2 + O2
_________________ CO O > 2CO2

25. 3. Single-Replacement
A single-replacement reaction is one in which one element replaces a second element in a compound
general form: Ao B+C Bo A+C-
Example: Zn + Cu+2(NO3) Cu + Zn+2(NO3)-1
general form: B+C Do B+D Co
Example: Na+Cl Br2 2 2
2Na+Br Cl2

26. 4. Double-Replacement general form: A+B- + C+D- ---> A+D- + C+B-
Ex.: Na+(CO )-2 + Ba+2Cl > 2Na+Cl-1 + Ba+2(CO )-2
Specific type: Neutralization
Ca(OH) HCl ---> CaCl H2O
base acid yields salt water
Specific type: Precipitation
Ag(NO3) NaCl ---> AgCl( ) + Na(NO3) 2 3 2 3

27. Classify each reaction as Single Replacement or Double Replacement
__________ Mg Ag2SO4 ---> MgSO Ag
__________ 2NaF + CaCO > Na2CO CaF2
__________ SrBr KOH > Ca(OH) KBr
__________ 2LiCl Br > Cl LiBr

28. Combustion Rxns Ex: CH4 + 2 O2 CO2 + 2 H2O
-a reactant (hydrocarbon) and oxygen, O react and release energy, heat, and/or light, and products formed are CO2 and H2O
Ex: CH O CO H2O

29. Endothermic and Exothermic Reactions
We can indicate if energy was present in the reaction
Reactions that have energy as a reactant are called endothermic
- They require energy for the reaction to occur
- Also sometimes represented as → or →
Reactions that have energy as a product are called exothermic
- Energy happens as a result of the reaction
heat

30. Predicting Products of chemical reactions

31. 5 types of Reactions
Synthesis – Forms one product from two or more reactants
general equation: A B AB
Example: Fe O Fe2+O2-
(Bring 1 of each element over and balance charges of each element)
Balance: 2
Fe O FeO 2

32. You Try 2 K + F2 ----> 2 K F Ca + Br2 ----> Ca Br 2+1 -1 +2
Ca Br >
Ca Br -1 2 +2 2
Ba O > 2
Ba O -2

33. Decomposition- Breaks down one reactant.
General Equation: AB > A + B
Example: CuO > Cu + O2
Balanced: 2CuO > 2Cu + O2

34. You Try
K I > 2 2
K I 2 2
CaO > 2
Ca O 2

35. Metal Chlorate --------> Metal Chloride + Oxygen
Example: KClO > K+1Cl O2
(Charges must be checked for the metal chloride)
Balanced: 2KClO > 2KCl O2
Metal Carbonate > Metal Oxide + Carbon Dioxide
Example: Na2CO > Na+1O CO2
(Charges must be checked for the metal oxide)
Balanced: Na2CO > Na2O CO2

36. You Try 2 2 3 Rb2(CO3) ----> Rb O + CO2 Li(ClO3) ----> Li Cl+1 -2
+ CO2 2 2
Li(ClO3) ----> 2
Li Cl +1 -1 3
+ O2

37. Single Replacement - One element is replaced with another element
General Equations: A + BC > B + AC
BC + D > BD + C
Cation being replaced:
Example: Na + MgCl >
(Charges must be checked for the new compound)
Balanced:
Anion being replaced:
Example: F2 + HCl >
Mg + Na Cl +1 -1 2
Na + MgCl > Mg + NaCl 2
Cl H F +1 -1 2
F HCl -----> Cl HF 2 2

38. Try 2
Na + Mg(CO3) ---> Mg
+ Na (CO3) +1 -2 2

39. Double Replacement- Two elements are replaced with two elements
(Ionic Equations) The two cations switch places.
General equation: AB + CD > CB + AD
Example: MgSO4 + K2CO > K+1SO Mg+2CO3-2(s)
Balanced: MgSO4 + K2CO > K2SO MgCO3(s)
Neutralization
Precipitate

40. Try 2 +2
+ Na (SO4) -1 -2
NaNO3 + Ca(SO4) --->
Ca (NO3) +1 2 2

41. Combustion: Produces fire
General Equation: Hydrocarbon + Oxygen ---> Carbon Dioxide + Water
Example: C3H8 + O > CO2 + H2O
Balanced: C3H8 + 5O > 3CO2 + 4H2O
CHARGES DO NOT NEED TO BE CHECKED, JUST BALANCE !!!

42. Directions: Write the formulas for the reactants.
Identify the type of reaction.
Predict the products, make sure the formulas are correctly formed.
Identify Diatomic elements
Balance the equation.

43. Aluminum chloride ---> C2H6 + Oxygen ---> (Ethane) Iron + Lead II Nitrate --->

44. Barium Nitrate + Lithium Phosphate ---> Aluminum hydroxide + sulfuric acid --->

45. Do Now Predict the products and identify the type of reaction.
Determine if a neutralization reaction has occurred or if a precipitate has formed.
Aluminum + iron (III) oxide --->
Sodium plus hydrogen --->
Silver nitrate plus zinc chloride
Potassium carbonate --->

46. Do Now What does it mean when an element like calcium burns in air?
What other reaction type requires some heating for the reaction to occur?

47. Do Now Adding O2 to the reactant Decomposition
What does it mean when an element like calcium burns in air?
What other reaction type requires some heating for the reaction to occur?
Adding O2 to the reactant
Decomposition