1. Lesson Tasks
Complete the Chemical Equations worksheet using the information in this PPT.
Take 1 page of notes, highlighting key point
Answer review questions on slide:
Chemical Reactions Video with Transcript Annotation
Files are on the Class Website

2. Chemical Equations & Reactions
Objective:
To write balanced chemical equations by inspection.
Balanced chemical equation:
– Provides qualitative information about the identities and physical states of the reactants and products
– Provides quantitative information because it tells the relative amounts of reactants and products consumed or produced in the reaction
– The number of atoms, molecules, or formula units of a reactant or product in a balanced chemical equation is the coefficient of that species
– Mole ratio of two substances in a chemical reaction is the ratio of their coefficients in the balanced chemical equation
Chemical Equations & Reactions

3. Chemical Reactions You should be able to Classify reactions by type.
Write a balanced molecular equation, complete ionic equation, and a net ionic equation.
Balance oxidation-reduction reactions.
Predict if a precipitate will form using the solubility rules.
Predict products of reactions given the chemical names of the reactants.

5. Organize Your Thoughts
Chemical
reactions
Chemical
equations
Chemical
equations
Synthesis
Decomposition
Single replacement
Double replacement
Combustion
Balancing equations
Predicting products from reactants

6. Describing a Chemical Reaction
Indications of a Chemical Reaction
Evolution of heat, light, and/or sound
Production of a gas
Formation of a precipitate
Color change

7. Signs of Chemical Reactions
There are five main signs that indicate a chemical reaction has taken place:
release
input
change in color
change in odor
production of new
gases or vapor
input or release
of energy
difficult to reverse

8. Chemical Equations Depict the kind of reactants and products
aluminum oxide
Depict the kind of reactants and products
and their relative amounts in a reaction.
4 Al(s) O2(g) Al2O3(s)
Objectives:
To explain the concept of an activity series for metals.
To predict whether a single-replacement reaction occurs by referring to the activity series.
The Activity Series
– Predicts the outcome of the single-displacement reactions
– Arranges metal and hydrogen in decreasing order of their tendency to be oxidized
– Active metals at the top of the series have the greatest tendency to lose electrons; these including alkali metals (Group 1), alkaline earths (Group 2), and Al (Group 13).
– Inert metals at the bottom of the series have the lowest tendency to be oxidized; these include precious metals or coinage metals located in the lower-right portion of the metals in the periodic table.
– Any element will reduce compounds of the elements below it in the series.
– Only those metals that lie above hydrogen in the activity series dissolve in acids to produce H2.
The letters (s), (g), and (l) are the
physical states of compounds.
The numbers in the front are called
stoichiometric coefficients.

9. Chemical Equations 4 Al(s) + 3 O2(g) 2 Al2O3(s)
aluminum oxide
sandpaper
4 g Al g O2 yield 2 g Al2O3
This equation means:
4 Al atoms O2 molecules yield 2 molecules of Al2O3 or
4 Al moles O2 moles yield 2 moles of Al2O3
4 mol
3 mol
2 mol
108 g g = g

10. Chemical Equations The Law of Conservation of Matter
Because the same atoms are present
in a reaction at the beginning (reactants)
and at the end (products), the amount
of matter in a system does not change.
CHEMICAL EQUATION indicates the reactants and products of a reaction.
The Law of Conservation of Matter
20%
100%
Chemical
Factory
100%
80%
REACTANTS → PRODUCTS
Kotz web

11. Chemical Equations
Because of the principle of the conservation of matter,An equation must be balanced.
It must have the same number of atoms
of the same kind on both sides.
Lavoisier, 1788 “Father of Modern Chemistry”

12. Characteristics of Chemical Equations
The equation must represent known facts.
The equation must contain the correct formulas for the reactants and products.
The law of conservation of mass must be satisfied.

13. Word Equations
A WORD EQUATION describes chemical change using the names of the reactants and products.
Write the word equation for the reaction of methane gas with oxygen gas to form carbon dioxide and water.
methane oxygen
carbon dioxide water
Reactant
Product
CH4 + 2 O2
CO2 + 2
H2O

14. Unbalanced and Balanced EquationsH Cl Cl H Cl Cl H H
H2 + Cl2 → HCl
(unbalanced)
H2 + Cl2 → 2 HCl
(balanced)
reactants products H Cl
reactants products H Cl 2 1 2 2 2 1 2 2

15. Visualizing a Chemical Reaction2
Na Cl NaCl 2
___ mole Na 10 10
___ mole Cl2 5 5
___ mole NaCl 10 10 ?

16. Visualizing a Chemical Reaction2
Na Cl NaCl 2

17. Meaning of Chemical Formula
Symbol Meaning Composition
H2O One molecule
of water:
Two H atoms and one O atom
2 H2O Two molecules
of water:
Four H atoms and two O atoms
H2O2 One molecule
of hydrogen
peroxide:
Two H atoms and two O atoms

18. Balancing Chemical Equations
Balanced Equation – one in which the number of atoms of each element as a reactant is equal to the number of atoms of that element as a product
What is the relationship between conservation of mass and
the fact that a balanced equation will always have the same
number of atoms of each element on both sides of an equation?
Determine whether the following equation is balanced.
2 Na + H2O → 2 NaOH + H2
2 Na H2O → 2 NaOH + H2

19. Balancing Chemical Equations
Write a word equation for the reaction.
Write the correct formulas for all reactants and products.
Determine the coefficients that make the equation balance.

20. Balancing Chemical Equations
Other examples
NO(g) + O2(g) → NO2(g)
is it balanced?
Is this balanced?
NO(g) + O(g) → NO2(g)
Is this OK?
A reaction that yields an insoluble product, a precipitate, when two solutions are mixed
Are a subclass of exchange reactions that occur between ionic compounds when one of the products is insoluble
Used to isolate metals that have been extracted from their ores and to recover precious metals for recycling
Is this balanced?
NO(g) + ½ O2(g) → NO2(g)
Is this OK?

21. Balancing Chemical Equations
An important point to remember
2 NO(g) + O2(g) → 2NO2(g)
The 2 to the left of NO(g) and NO2(g) refers to the number of molecules present in the balanced equation.
It is a “multiplier” for every atom in the molecule.
A reaction that yields an insoluble product, a precipitate, when two solutions are mixed
Are a subclass of exchange reactions that occur between ionic compounds when one of the products is insoluble
Used to isolate metals that have been extracted from their ores and to recover precious metals for recycling
The subscript 2 in O2 (g) and NO2(g) refers to the number
of atoms of this type that are present in each molecules
(or ionic compound).

22. Showing Phases in Chemical Equations
Solid Phase – the substance is relatively rigid and has a definite volume and shape. NaCl(s)
Liquid Phase – the substance has a definite volume, but is able to change shape by flowing. H2O(l)
Gaseous Phase – the substance has no definite volume or shape, and it shows little response to gravity. Cl2(g)
H2O(s) H2O(l) H2O(g)

23. Additional Symbols Used in Chemical Equations
“Yields”; indicates result of reaction
Used to indicate a reversible reaction
A reactant or product in the solid state;
also used to indicate a precipitate
Alternative to (s), but used only to indicate a precipitate
A reactant or product in the liquid state
A reactant or product in an aqueous solution
(dissolved in water)
A reactant or product in the gaseous state
(s)
(l)
(aq)
(g)

24. Additional Symbols Used in Chemical Equations
Alternative to (g), but used only to indicate a gaseous product
Reactants are heated
Pressure at which reaction is carried out, in this case 2 atm
Pressure at which reaction is carried out exceeds normal
atmospheric pressure
Temperature at which reaction is carried out, in this case 0 oC
Formula of catalyst, in this case manganese (IV) oxide,
used to alter the rate of the reaction Δ
2 atm
pressure
0 oC
MnO2

26. Formation of a solid: AgCl
AgNO3(aq) + KCl(aq) → KNO3 (aq) + AgCl(s)

27. Pb2+ Cl1- K1+ I1- Pb2+ Cl1- K1+ I1- Cl2 Pb I K KCl PbI2 + +
lead (II) chloride potassium iodide
potassium chloride +
lead (II) iodide
Pb2+
Cl1-
K1+
I1-
Pb2+
Cl1-
K1+
I1-
Cl2 Pb + I K
KCl +
PbI2
(aq)
(ppt)

28. Potassium reacts with Water
P O W !

29. Meaning of Coefficients
2 atoms Na
1 molecule Cl2
2 molecules NaCl
2 Na + Cl NaCl
2 g sodium +
1 g chlorine =
2 g sodium chloride
2 mol sodium
1 mol chlorine
2 mol sodium chloride
(2 mol Na) x (23 g/mol)
(1 mol Cl2) x (71 g/mol)
(2 mol NaCl) x (58.5 g/mol)
46 g
71 g
117 g
What you should learn:
In chemical change atoms are rearranged but no atoms are created and none are destroyed
Chemical equations are symbolic representations of what is happening at the molecular level and are used to communicate the conditions under which a reaction proceeds, the products and amount of energy that results, and allow for predictions to be made.
More Specifically...:
Classify those equations that come under the heading of synthesis, decomposition, single replacement, double replacement, neutralization, oxidation/ reduction and combustion
Identify and name acids and bases
Use principle of conservation of mass to balance a reaction
From a written description of a reaction write a balanced reaction using correct state symbols
Show that the conservation of mass is true for a balanced reaction
Predict the products of chemical reactions (including state symbols) when given the reactants.
Use an activity series to predict the spontaneity of reactions.
Use solubility rules to predict the formation of a precipitate
Define oxidation and reduction, and identify any species undergoing oxidation or reduction, and identify the oxidizing and reducing agents
Write half reactions for single replacement reactions (monoatomic ions only)
Fast Track to a 5 (page 61)
To know how to calculate the molecular mass of a covalent compound and the formula mass of an ionic compound
To be able to use the concepts of the mole and molar mass to calculate the number of atoms, molecules, or formula units in a sample of a substance
To be able to determine the empirical formula of a compound from its composition by mass
To know how to derive the molecular formula of a compound from its empirical formula
To be able to describe a chemical reaction
To know how to calculate the quantities of compounds produced or consumed in a chemical reaction
To identify fundamental types of chemical reactions
To begin to predict the types of chemical reactions that substances undergo
117 g

30. Classes of Reactions Chemical reactions Precipitation reactions
Oxidation-Reduction
Reactions
Acid-Base
Reactions
Combustion
Reactions

31. Summary of Classes of Reactions
Chemical reactions
Precipitation
reactions
Oxidation-Reduction
Reactions
Acid-Base
Reactions
Combustion
Reactions
Synthesis
reactions
(Reactants are
elements.)
Decomposition
reactions
(Products are
elements.)

32. A Mixture of Molecules

33. Review Questions Define catalyst.
What information is found in an equation?
What symbols are used to represent the states of matter?
What is the meaning of “aq”?
How do you indicate a catalyst is being used in a reaction?
What is activation energy?
What the three things does conservation of matter require of chemical equations?
What is the procedure for balancing a chemical equation?
What is a synthesis reaction?
How is a combustion reaction related to a synthesis reaction?
What type of reaction is an explosion?
Compare decomposition and dissociation.
What determines whether one metal will replace another in a single displacement reaction?
What is the general form of a double displacement reaction?