1. Topic 2: Formulas and Equations
Chemical Symbols
- Each element has a one, two or three letter symbol to represent it
- Symbols with more than one letter are always written capital letter then lower case letter
- Based on IUPAC system of naming
Diatomic molecules
- elements found only combined covalently in nature
H2, N2, O2, F2, Cl2, Br2, I2

2. Element vs. Compound
Element
- Atoms of all the same type
Cannot be chemically broken down into two different substances.
Na Cu
Compound
Combination of elements
NaCl CuSO4
a. All sample of a compound have the same properties
b. Atoms in a compound are in a simple ratio
c. All areas of a compound are the same

3. What two elements do you think are found in a quarter?
What’s in a Quarter?
What two elements do you think are found in a quarter?
(Write the name an symbol below.
What do you think will happen when the RED HOT quarter is placed into the beaker of methanol?
Describe what did happen?
Materials:
19.4 MB
US quarter (pre-2000)
methanol 100 mL
beaker, 150 mL
watch glass (to cover
propane or butane torch, or Bunsen burner
tongs
Procedure: Use a torch or hot Bunsen burner to heat the quarter very hot. It needs to be as red-hot as possible. When peak temperature has been reached, immediately drop the red-hot quarter into a 150 mL beaker containing 100 mL of methanol. If the methanol ignites when the coin is dropped in, cover it with the watch glass to extinguish the flames.
As soon as the quarter is dropped in it will boil the methanol. In a few moments the methanol will stop bubbling. A short time later a phase transition takes place which will
release heat. Another rush of bubbles will be
seen as more methanol boils. The quarter will grow pink as a layer of copper migrates up through the nickel coating.
Is the reaction that took place exo or endothermic/
Why did the quarter change color?

5. Chemical Formulas Chemical formulas tell us two things
Type of elements present
Number of atoms
Subscript-
Indicates number of atoms
Examples
MgBr2
1 Mg for every 2 bromines
Al2O3
2 aluminums for every 3 oxygens
Ca(OH)2
1 calcium , 2 hydrogens and 2 oxygens
2 sets of OH
Example - How many sulfur atoms are present in Pb(SO4)2? 2
How many oxygen atoms are present?
4 x 2 = 8

6. Coefficients
-numbers placed in front of a chemical formula to indicate how many molecules are present
MgS
Ex.
MgS
6 MgS
MgS
MgS
MgS
MgS

7. What is the total number of molecules in this equation?
Burning Money!!!!
Examine the following equation and answer the questions that follow
2 C3H7OH(l) + 9 O2(g) → 6 CO2(g) + 8 H2O(g) ∆Hrxn = kJ/mol
What is the total number of molecules in this equation?
How many atoms of oxygen are in the equation?
55ml isopropyl alcohol mixed with 45 ml water. United States currency is not “paper” money; rather, it is manufactured from cotton. The cotton fibers preferentially absorb the water in the solution mixture, which prevents it from being burned. However, the flame must be put out as the flames subside in order to prevent the water from evaporating and burning the bill. The water in the mixture also acts to absorb some of the energy from the reaction
Describe the reaction as either exothermic or endothermic.

8. - Water gets trapped in the crystal structure of some ionic compounds
Hydrates
- Water gets trapped in the crystal structure of some ionic compounds
The same amount of water is found in the crystal all the time
Ex. CuSO4* 5H2O
* Does not mean multiply!!! It means it is an hydrate!

9. Types of Chemical Formulas
Molecular Formula
Tells us how many atoms of each element are
needed to form the molecule
Examples
C2H6
-ethane - 2 C : 6H
Empirical Formula
Shows the simplest ratio of atoms
C2H6
CH3
Molecular
Empirical
C3H6
CH2
Sometimes the empirical formula and the molecular formula are the same
CO2
H2O

10. Which of the following are empirical formulas?
A. H2O2 B. CO C. P2O4 D. Al2O3
What is the empirical formula of the following?
C6H12O6 Hg2O PbSO4
PbSO4
CH2O
HgO2

11. Writing Chemical Formulas
When Ba is combined with Cl, is the formula BaCl?
Or ClBa?
Or Cl2Ba?
Or Ba2Cl?
Based on OXIDATION NUMBERS

12. Oxidation numbers -
Indicate the number of electrons lost or gained in a bond
Oxidation number
Negative oxidation number
Atom gains partial or total control of electrons
Positive oxidation number
Atom loses partial or total control of electrons

13. Rules for Writing Formulas
The element or ion with the positive oxidation state
(the metal) is written first
Write in the oxidation states, then write out who comes first. Mg Br +2 -1 -1 +2 Ca Cl -2 +? Cu O +1 -2 Li S

14. Add one more Cl-1 to get to zero +1 -2 H2O H O Li S +1 -2 Li2S
2. The oxidation states of all elements in a compound must add up to zero
-For every electron lost, it must be gained by another atom
Example Cl -1 -1 +2 Ca Cl
CaCl2
Loses control of 2 e-
Gains control of 1e-
2 e-
Add one more Cl-1 to get to zero +1 -2
H2O
H O
Li S +1 -2
Li2S
3. Polyatomic ions are treated as one element +2 -2
Ca SO4
Na PO4
CaSO4 +1 -3
Na3PO4

15. 4. If a polyatomic ion is used more than once, put parentheses around it+2 -1
Ca(OH)2
Ca OH
NH4 SO3 +1 -2
(NH4)2SO3
Practice
Li+1
O-2
Li2O
Lithium oxide
Magnesium iodide
potassium phosphate
ammonium nitrate
aluminum oxide
calcium phosphate
Mg+2 I-
MgI2
K+1
PO4-3
K3PO4
NH4+
NO3-
NH4NO3
Al2O3
Al+3
O-2
Ca3(PO4)2
Ca+2
PO4-3

16. Nomenclature
Naming compounds
1. Binary Compound
Consists of 2 different elements
To name these, use the name of the first atom, remove “ine” from the second atom and add “IDE”
NaCl Na__________ Cl_________
NaCl _____________________

17. You must know the –ide names for the following
Hydrogen
Hydride
Oxygen
Oxide
Bromine
Bromide
Iodine
Iodide
Fluorine
Flouride
Nitrogen
Nitride
Selenium
Selenide
Sulfur
Sulfide

18. Examples
MgBr LiO
SrO AlI3
NaF ZnS
Magnesium bromide
Magnesium bromine
Lithium oxide
Strontium oxygen
Strontium oxide
Aluminum iodide
Sodium fluoride
Zinc sulfide
2. Ternary compounds
Compounds with 3 or more elements
-usually a metal with a
POLYATOMIC ION

19. Polyatomic ion
Group of atoms bonded together to obtain
an overall charge
Has special properties unlike the individual atoms -3 O |
O - P - O
Often acts as one atom
Found on Table E
PO4-3
phosphate
Name the following polyatomic ions
NH4+
SO3-2
OH-
CO3-2
sulfite
hydroxide
carbonate
ammonium
Polyatomic ions bond IONICALLY with other ions

20. Naming compounds with polyatomic ions
- Do not change any parts, take the name of each part of the compound
-Circle the polyatomic ion in each compound, then name the compound
MgSO4 NaSCN
LiOH NH4OH
CaCO3 Li2SO3
Al(OH)3
Magnesium sulfate
Sodium thiocyanate
Lithium hydroxide
Ammonium hydroxide
Calcium carbonate
Lithium sulfite
Aluminum hydroxide

21. Naming Covalent Compounds
-compounds with only nonmetals
-using Table S, write the name of the element with the lower electronegativity first
-use prefixes to tell how many of each element are present
Ex.
CO2
Carbon dioxide
2.6
3.4
2 oxygen's
N2Cl2
Dinitrogen dichloride
3.0
3.2

22. Try: Carbon tetrachloride
Diphosphorous pentoxide

23. Name the following Compounds
LiBr
MgSO4
CaCO3
SrCrO4
ZnS
Al2(SO4)3
NH4NO3
Write the empirical formula
C6H12O6
P2O4
C2H2
PbCl4
H2O2

24. Write out the following formulas
Calcium oxide
Lithium Sulfide
Lithium Sulfate
Magnesium phosphate
Aluminum carbonate
Nitrogen dioxide

25. STOCK SYSTEM
So far, we have learned how to take different elements and combine them together to make a compound.
But there are some elements that have several oxidation states.
For example, what is the formula for lead oxide?
Pb has two oxidation states Pb+2 and Pb +4
Pb+2
O-2
Pb+4
O-2
O-2
PbO
PbO2
Which of the two is correct?
BOTH are correct!
How can we have two different formulas with the same name?
We need a way to distinguish between these two.

26. Stock System CuO MgO LiNO3 NO CaSO4 Ni(NO3)2 ZnCO3 NO NO Yes NO Yes NO
- used when the first part of a compound (the positive one) has two or more positive oxidation states.
Which of the following requires the stock system?
CuO MgO LiNO3
NO CaSO Ni(NO3)2 ZnCO3 NO NO
Yes NO
Yes NO
Yes

27. How is the stock system used?
1. Assign oxidation numbers to the elements in the compound
2. Write the oxidation state of first element as a roman numeral
Pb+4
O-2
Pb+2
O-2
O-2
PbO
PbO2
Pb is in the +2 state, so it is called
Pb is in the +4; state, so it is called
Lead (II) oxide
Lead (IV) oxide +2 -1
SnCl2
Sn has an oxidation state of +2 or +4. +2 -2
= 0
The Cl must be in the -1 state, since Sn must be a positive oxidation state,
Since there are two Cl’s, the Sn must be in the +2 oxidation state to cancel out the Cl’s
Tin
(II)
Chloride

28. Practice - All of the following compounds need the stock system
Practice - All of the following compounds need the stock system. Determine the oxidation state of the cation (the first ion) and write out the name. +1 -1
Copper (I) nitrate
CuNO3
NiF2
HgO
Hg2O
FeCl3
NO2 +2 -1
Nickel (II) fluoride +2 -2 +2 -2
Mercury (II) oxide +1 -2
Mercury (I) oxide +2 -2 +3 -1
Iron (III) chloride +3 -3 +4 -2
Nitrogen (IV) oxide +4 -4

29. Writing Formulas with the Stock System
If we are given a chemical name that uses the stock system, how do we write the formula?
Example - What is the chemical formula for
Copper (II) oxide?
We know that the compound contains copper and oxygen
And we know that oxygen must take a -2 oxidation state +2 -2 O Cu
Don’t have to look up copper. The (II) tells us that it is in the +2 state

30. CuO What is the chemical formula for copper (II) oxide?
What is the formula for Nickel (III) sulfate? +3 -2
According to chart E! Ni
SO4 Ni
(SO4) 2 3

31. Now write out the formulas for the following.
Nitrogen (II) chloride
Iron (III) oxide
Lead (IV) carbonate
Copper (I) sulfate
N+2
Cl-1
NCl2
Fe+3
O-2
Fe2O3
Pb+4
CO3-2
Pb(CO3)2
Cu+1
SO4-2
Cu2SO4

32. __Chemical Equations - Shows what happens during a chemical reaction
The chemicals involved
How many of each molecule
Energy used, phases
Reactants
Substances that exist before the reaction takes place
Always found on the left, or facing away from the arrow
Products
Substances that exist after a chemical reaction
Always found on the right, or facing the arrow head
The reaction arrow is the “ “. It is always found in the middle of a chemical reaction and it divides up the reactants and the products

33. Examples - List the reactant and the products of the following reactions
Reactants Products
2 H2 O2
2 H2O
a. 2 H2 + O H2O
HCl
NaOH
NaCl
H2O
b. HCl + NaOH H2O + NaCl

34. ? Balancing a chemical equation CO + O2 CO2
How many carbon atoms are on each side of the equation? 1
How many oxygens are on each side of the equation?
Three on the reactants, but only 2 one the products side
Is this possible? ?
No, something must happen to the other oxygen O =
C=O O = O O O O

35. We need another CO for the other oxygen to attach to.=
C=O O =
So two molecules of CO combine with one molecule of O2 O O O O O O O =
C=O
2 CO + O CO2 O O
2 C
4 O
2 C
4 O
Now the equation is balanced because we have the same number and types of atoms on both sides

36. Step 1: Write the word equation
Problem 1: Write the balanced equation for the reaction between aluminum sulfate and calcium chloride to produce aluminum chloride and a white precipitate of calcium sulfate.
Step 1: Write the word equation
Aluminum sulfate + Calcium chloride  Aluminum chloride + Calcium Sulfate
Step 2: Replace the words with the correct formulas
Al2(SO4)3
CaCl2
AlCl3
CaSO4 
Step 3: Adjust coefficients to make the equation balance. Use trial and error until both sides have same number of each element.
Al2(SO4) CaCl2  AlCl CaSO4

37. This is a hit and miss procedure
This is a hit and miss procedure. Often you will need to change the coefficients several times in order to balance the equation correctly
Remember to only change the coefficients, not the molecular formula
Examples 2 3
a. ____ NH _____ N2 + ____ H2
b. ____ Li2SO4 + ____ Na ____ Na2SO4 + ____ Li
c. ____ HCl + ____ Mg ____MgCl2 + _____ H2 2 2 2

38. Important point -Some pure elements must exist as DIATOMIC molecules H
Pure hydrogen gas is H2 N
Pure nitrogen is N2
This occurs for the following elements
H, N, O, F, Cl, Br, I
Example - Balance the following equation
Nitrogen + oxygen nitrogen (II) oxide
N2 + O2 2 NO

39. Showing Energy changes in Reactions
A. Reactions that require energy are endothermic
Ex. 2 H2O + energy  2 H2 + O2
B. Reactions that give off energy are exothermic
Ex. 2 H O2  2 H2O + energy

40. Write the formulas for the following compounds
Match-Making
The first matches were invented in 1827 by chemist John Walker. He determined that a wood splint tipped with antimony (II) sulfide, potassium chlorate, gum and starch could be ignited by striking it against a rough surface.
Write the formulas for the following compounds
Antimony (II) sulfide
Potassium chlorate
Describe the reaction that took place when Mr. Stone lite the mixture on fire.
Materials: potassium chlorate, KClO3, 0.5 g
sulfur powder, 0.5 g
fireproof lab mat or board
barbeque lighter
evaporating dish
Procedure: Carefully crush the potassium chlorate into a fine powder. Place it into the evaporating dish and add the sulfur powder. Gently stir the mixture in the evaporating dish until homogeneous.
Pour the mixture onto the lab mat and shape into a thin line. Ignite with the barbeque lighter held at arms length.
Was the reaction exo or endothermic and explain why.
Why safety matches?
Combustible materials are separated between match and striking surface

41. Balance the following equations
_____ KNO3 + _____ Na2SO4  _____ K2SO4 + _____ NaNO3
_____ H2 + _____ Cl2  _____ HCl
_____ Li + _____ O2  _____ Li2O
_____ HgO  _____ Hg + _____ O2
_____ AlBr3 + _____ Cl2  _____ AlCl3 + _____ Br2

42. Nitrogen + oxygen  nitrogen(IV) oxide
Barium chloride + sodium sulfate  barium sulfate + sodium chloride
Magnesium + sulfuric acid  magnesium sulfate + hydrogen gas
Potassium + water  potassium hydroxide + hydrogen gas
Aluminum + hydrochloric acid  aluminum chloride + hydrogen gas

43. Types of Chemical Reactions
There are four basic types of chemical reactions
Observe the products and the reactants to determine the type of reaction.
A. Synthesis
Two or more compounds combine together to produce one compound
Ex.
A + B --> AB
Examples
2 H2 + O2 --> 2 H2O 2
Mg + O2 --> 2
MgO

44. Exothermic reaction of Calcium oxide and water

45. B. Decomposition
Single compound breaks down into 2 or more compounds
AB --> A + B
Examples
2 H2O --> 2 H2 + O2 2
NaCl --> 2 Na +
Cl2
C. Single Replacement
Element + Ionic Compound
Element + Ionic Compound
X + AB  A + XB
Ex. Zn CuSO4  ZnSO4 + Cu

46. What does an elephant use to clean it’s teeth?
Elephant toothpaste
Balance the equation below
H2O2(aq) → H2O(g) + O2(g) + energy
What if the name of the H2O2 (you’ll need to use table E)
We’ve talked of many types of reactions at this point. Use to types that we’ve talked about during this unit to describe the reaction above.
Materials: hydrogen peroxide, H2O2, 30% 20 mL
dishwashing soap, 10 mL
sodium iodide solution, NaI, 2M, 5 mL
graduated cylinder 100 mL
graduated cylinder 10 mL
spill tray
wooden matches
Procedure: pour 20 mL of 30% hydrogen peroxide into the 100 mL graduated cylinder. Use gloves and safety glasses as the peroxide is corrosive to skin and can cause burns. Add 10 mL of dishwashing soap to the graduated cylinder.
When ready for the presentation, place the graduated cylinder in the spill tray. Point out to the audience that hydrogen peroxide will slowly decompose on its own, although the rate is very slow, as can by seen by the lack of bubbles in the graduated cylinder. Add the 5 mL sodium iodide solution. Within 5 to 10 seconds a large column of foam will rapidly rise up the graduate and erupt out of the cylinder. Steam and heat will also be produced. The foam contains a lot of oxygen which can be illustrated by pushing a burning match into the foam. Instead of going out, the flame grows larger.
Discussion: The catalytic decomposition of hydrogen peroxide is exothermic, as can be seen from the steam. The catalyst acting in this reaction is the iodine ion, which is not changed or used up in the reaction: I
- (aq)
2 H2O2(aq) → 2 H2O(g) + O2(g) + energy
It is the oxygen gas and water vapor that cause the dishwashing soap to foam up.

47. D. Double Replacement
2 compounds in solution are mixed C C C
Ex.
AB + CD --> CB + AD C A B C A D A A A
Watch the oxidation states when making new compounds!
NaCl(aq) + AgNO3(aq)
NaNO3(aq) + AgCl(s)
Al(OH)3
NaI 3
AlI NaOH 3

48. Synthesis reaction – fog machine
Synthsis pg 113
Pg 117 synthesis
Single and double replacement 123
Elephant toothpaste decomp

49. Unknown Reactants and Products
-since matter can NOT be created or destroyed, you must always have the same number of each type of element on each side of the equation
-if you have a balanced equation you should be able to figure out what the unknown product or reactant is
EX.
H2SO NaOH  Na2SO WHAT?
BaCl2 + K2CO3  WHAT? + BaCO3
2 NaHCO3  Na2CO3 + H2O WHAT?

50. Determining Missing Mass in an Equation
RULE: Total mass of reactants = total mass of products
If 103.0g of KClO3 are decomposed to form 62.7 g of KCl and O2 gas according to the equation
2 KClO3  2 KCl + 3 O2
How many grams of oxygen are formed?
Total mass of reactants = g
Total mass of products = g
103.0 = mass of O g KCl
103.0 – 62.7g KCl = mass of O2

51. How many grams of silver nitrate are needed to react with 156
How many grams of silver nitrate are needed to react with 156.2g sodium sulfide to produce g silver sulfide and g sodium nitrate?
1. Rewrite and balance the equation.
2. Substitute masses in and solve for missing mass