1. Calculating Chemical Equations
Why and How Many Atoms Bond

2. Counting Atoms
A Chemical Formula shows how many of which atoms are in a molecule
A Subscript is a number placed below and behind a symbol to show how many of which atoms are present
H2O

3. Counting Atoms
A Coefficient is placed in front of a molecule to show more than one molecule
3H2O

4. H2 N2 O2 F2 I2 Cl2 Br2 Counting Atoms
A Diatomic Molecule shows two atoms of the same nonmetal (usually in gas form) that have bonded together
Reactive nonmetals will bond with one another if no other substance is available for bonding

5. Ca(OH)2 NH4Cl Polyatomic Ions A group of atoms that behave as one atom
Keep together as a unit
Listed on p. 619
If more than one polyatomic ion is present in a molecule, parentheses set it apart
Still use a subscript to show how many
Ca(OH)2
NH4Cl

6. Counting Atoms Write the molecule to be counted
List the participating atoms (or polyatomic ions) under the formula
Write all subscripts, including parentheses
Multiply by the coefficient
Some problems call for a total of atoms, some call for individual atoms

7. How many total atoms are in Methane, CH4?2 3 4 5 6

8. How many atoms of Chlorine are in Carbon Tetrachloride, CCl4?2 3 4 5 6

9. How many total atoms are in Magnesium Hydroxide, Mg(OH)2?3 4 5 6

10. How many atoms of Oxygen are in Acetic Acid, CH3COOH?2 3 4 5 6

11. How many total atoms are in Acetic Acid, CH3COOH?4 5 6 7 8 9

12. Oxidation Numbers
A positive or negative sign used to show what type of ion is formed after an atom has gained or lost enough electrons to be chemically stable
Written like a charge sign (upper right)
Always included with a list of polyatomic ions

13. BASE OXIDATION NUMBERS BY GROUP ±
USE ROMAN NUMERALS

14. What is the Oxidation Number for Sulphur (Group 16)?+1 +2 +3 4 -3 -2 -1

15. What is the Oxidation Number for Aluminium (Group 13)?+1 +2 +3 4 -3 -2 -1

16. What is the Oxidation Number for Potassium (Group 1)?+1 +2 +3 4 -3 -2 -1

17. What is the Oxidation Number for Chlorine (Group 17)?+1 +2 +3 4 -3 -2 -1

18. What is used to show the Oxidation Number for Transition Metals (Groups 3 – 12)?
Alchemical Symbols
Transition Icons
Arabic Numerals
Roman Numerals
Hieroglyphics
Kanji

19. Making formulæ “The Criss-Cross Method”
Write the element with the positive oxidation number
Write the element with the negative oxidation number
Rewrite the two symbols together below the symbols with their oxidation number
Drop the positive or negative sign
Write the oxidation number from one symbol on the other symbol as a subscript
Remember to add parentheses for polyatomic ions
Don’t write “1”s
Reduce any evenly-divisible subscripts

20. What is the correct formula for a bond between Carbon and Hydrogen?CH
C2H2
CH3
C2H3
CH4

21. What is the correct formula for a bond between Sodium and Nitrogen?
NaN
Na2N2
Na3N
Na2N3
Na3N4

22. What is the correct formula for a bond between Calcium and Chlorine?
CaCl
Ca2Cl2
Ca2Cl
CaCl2
Ca3Cl4

23. What is the correct formula for a bond between Sodium and Hydroxide?
NaOH
Na(OH)2
Na(OH)3
Na2(OH)3
Na(OH)4

24. What is the correct formula for a bond between Aluminum and Sulfate?
AlSO4
Al2(SO4)2
Al2(SO4)3
Al3(SO4)3
Al(SO4)4

25. Binomial Nomenclature
Naming a two-part name
Used to differentiate between Fluorine (an element) and Fluoride (part of a compound)
Never change the name of a Polyatomic Ion
Big difference between Sulfide and Sulfite

26. Ionic Compounds List the positive ion (or metal) first
Use Roman Numerals to show the Oxidation number of a transition metal
Begin the negative ion (or nonmetal), changing the ending to –ide
Oxide
Sulfide
Phosphide

27. Covalent Compounds Prefixes are used to show how many of which atoms
Prefixes are number-words from Greek & Latin
Write the name of the first atom
Add a prefix only if there is more than one of the first
Write the name of the second atom
Add a prefix showing how many of the second are present
Change the ending to -ide

28. Numbering Prefixes 1 – Mono- 2 – Di- 3 – Tri- 4 – Tetra-, 5 – Penta-
6 – Hexa-
7 – Hepta-
8 – Octa-
9 – Nona-
10 – Deka-

29. What is the name for N2O4? Nitrogen Oxide Dinitrogen Oxide
Dinitrogen Dioxide
Dinitrogen Tetraoxide
Nioxx (Nioxalate)

30. What is the name for Na2S? Sodium Sulfide Sodium Sulfite
Sodium Sulfate
Disodium Sulfide
Disodium Sulfate

31. What is the name for CO2? Carbon Oxide Carbon Dioxide Monocarbon Oxide
Monocarbon Dioxide
Mi-Bref (B-hot)

32. What is the name for (NH4)2O?
Nitrogen Hydrogen Oxide
Mononitrogen Tetrahydrogen Oxide
Ammonium Oxide
Diammonium Oxide
Ammonium Oxalate

33. Chemical Equations
A shorthand way to describe a chemical reaction using chemical symbols and formulæ

34. Chemical Equations Has three parts Reactants Products Yield Arrow
Substances present before the reaction
Products
Substances present after the reaction
Yield Arrow
Indicates the direction of a reaction
Some reactions are reversible

35. Writing a Chemical Equation
Chemical symbols give a “before-and-after” picture of a chemical reaction
Reactants Products
MgO C CO Mg
magnesium oxide to form carbon monoxide
reacts with carbon and magnesium

36. Balancing Chemical Equations
Equations must be balanced to observe the Law of Conservation of Matter
Matter can not be created or destroyed under normal reactions
If you begin a reaction with 5 g of Hydrogen, you must end up with 5 g of Hydrogen

37. A Balanced Chemical Equation
Same numbers of each type of atom on each side of the equation
Al S Al2S Not Balanced
2Al S Al2S Balanced

38. Balancing Chemical Equations
Count atoms on both sides of the yield arrow
Determine which elements are unequal
Use coefficients to balance the number of atoms on both sides
If you multiply one element in a compound, you multiply both elements in a compound
You can treat Polyatomic Ions as one if they appear on both sides of the equation
Go for the highest unequal elements first
Leave solitary elements for last

39. Steps in Balancing An Equation
Fe3O H Fe H2O
Fe: Fe3O H Fe H2O
O: Fe3O H Fe H2O
H: Fe3O H Fe H2O

40. Balancing Chemical Equations
Mg N Mg3N2
Al Cl AlCl3

41. Balancing Chemical Equations
Fe2O C Fe CO2
Al FeO Fe Al2O3
Al H2SO Al2(SO4) H2

42. Types of Chemical Reactions
Synthesis
Two or more substances form one new substance
H2 + O2  H2O
N2 + H2  NH3

43. Types of Chemical Reactions
Decomposition
One substance breaks down to form two or more new substances
PbCO3  PbO + CO2
H2CO3  H2O + CO2

44. Types of Chemical Reactions
Single Displacement
One substance replaces another in a compound
Li + AlCl3  LiCl + Al

45. Types of Chemical Reactions
Double Displacement
Two substances “swap partners” in two compounds
KOH + HBr  KBr + H2O
NaOH H2CO3  Na2CO H2O

46. Types of Chemical Reactions
Neutralization
Double-displacement reaction where an acid and a base form a salt and water
KOH + HBr  KBr + H2O
NaOH H2CO3  Na2CO H2O

47. Acids and Bases Acids Taste Sour Have a pH of less than 7
Produce Hydronium H3O+1 in solution
Have an “extra” H- on the beginning of the formula
H2SO4 – (Hydro)Sulfuric Acid
H3PO4 – (Hydro)Phosphoric Acid
HNO3 – (Hydro)Nitric Acid
HCl – Hydrochloric Acid

48. Acids and Bases Bases Taste bitter Have a pH of more than 7
Produce Hydroxide OH–1 in solution
Have an –OH on the end of the formula
NaOH – Sodium Hydroxide
KOH – Potassium Hydroxide
Ca(OH)2 – Calcium Hydroxide
NH4OH – Ammonium Hydroxide

49. Types of Chemical Reactions
Combustion
Where a carbon compound combusts with oxygen gas to form carbon dioxide and water
CH O2  CO H2O
C2H O2  CO H2O

50. Change in ENERGY Every reaction has some change in energy
Two possibilities:

51. Endothermic – absorbs energy from the environment to complete reaction
Feels “COLD” to its surroundings
Products have MORE energy than the reactants

53. Exothermic – releases energy to the environment as the reaction proceeds
Feels “HOT” to its surroundings
Products have LESS energy than reactants

55. Let’s get it started
Some reactions require a little “jump start” to proceed
Activation Energy
Energy required to be applied to start a reaction
Examples
Applying friction to start a match
The match causing a log to burn

58. Changes in Energy during reactions
Counting Atoms
Subscripts
Coefficients
Diatomic Molecules
Polyatomic Ions
Parenthesis
Oxidation Numbers
Binary Formulæ
Criss-cross method
Naming Rules
Ionic
Roman Numerals
Covalent
Prefixes
Balancing Equations
NEVER change subscripts
Law of Conservation of Matter
Types of Reactions
Changes in Energy during reactions