1. Chemical Equations & Reactions
Chemical Reaction - Study Questions
1. What is a chemical reaction?
2. What is evidence a reaction has occurred?
3. What is a chemical equation?
4. Define reactants.
5. Define products.
6. Define catalyst.
7. What information is found in an equation?
8. What symbols are used to represent the states of matter?
9. What is the meaning of “aq”?
10. How do you indicate a catalyst is being used in a reaction?
11. What is activation energy?
12. What the three things does conservation of matter require of chemical equations?
13. What is the procedure for balancing a chemical equation?
14. Balance the equation for the reaction of magnesium chloride and silver nitrate to form magnesium nitrate and silver chloride.
15. What is a synthesis reaction?
16. How is a combustion reaction related to a synthesis reaction?
17. What type of reaction is an explosion?
18. Compare decomposition and dissociation.
19. What determines whether one metal will replace another in a single displacement reaction?
20. What is the general form of a double displacement reaction?
21. What type of reaction is each of these?
2Na(s) + Cl2(g)  2NaCl(s)
PCl5(s)  PCl3(s) + Cl2(g)
2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s)
C6H12O6(s) + 6O2(g)  6CO2(g) + 6H2O(l)
BaCl2(aq) + H2SO4(aq)  2HCl(aq) + BaSO4(s)
22. What is the oxidation number of an element?
23. What is the oxidation number of the fluorine ion?
24. What is the sum of the oxidation numbers in a compound?
31. Can a redox reaction form a molecule? Explain your answer.

2. 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.
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

3. Organize Your Thoughts
Chemical
reactions
Chemical
equations
Chemical
equations
To identify the reactants and products in a chemical equation.
To balance a chemical equation with coefficients.
To identify synthesis (combination), decomposition, and combustion reactions.
To identify single-replacement reactions.
To identify double-replacement reactions.
To predict the products of a reaction.
Synthesis
Decomposition
Single replacement
Double replacement
Combustion
Balancing equations
Predicting products
from reactants
Packard, Jacobs, Marshall, Chemistry Pearson AGS Globe, page 175

4. 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
Objective:
To state four observations that are evidence for a chemical reaction.
Photo of precipitate:

5. 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

6. 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.
reactants
product
4 Al(s) O2(g) Al2O3(s)
A chemical equation is an expression that gives the identities and quantities of the substances in a chemical reaction
Chemical formulas and other symbols are used to indicate the starting material(s) or reactant(s), which are written on the left side of the equation, and the final compound(s) or product(s), which are written on the right side. An arrow, read as yields or reacts to form, points from the reactants to the products.
Abbreviations are added in parentheses as subscripts to indicate the physical state of each species:—(s) for solid, (l) for liquid, (g) for gas, and (aq) for an aqueous solution.
A balanced chemical equation is when both the numbers of each type of atom and the total charge are the same on both sides. A chemical reaction represents a change in the distribution of atoms but not in the number of atoms.
The letters (s), (g), and (l) are the
physical states of compounds.
The numbers in the front are called
stoichiometric coefficients.

7. Chemical Equations 4 Al(s) + 3 O2(g) 2 Al2O3(s)
aluminum oxide
sandpaper
4 Al(s) O2(g) Al2O3(s)
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

8. Chemical Equations 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.
The Law of Conservation of Matter
Law of Conservation of Matter means that nothing is “lost” or “stolen”. In the real world retail theft costs business lots (much of the theft is actually employee theft)!
20%
100%
Chemical
Factory
100%
80%
Kotz web

9. 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

10. 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.

11. Chemical Equations
Reactants – the substances that exist before a chemical change (or reaction) takes place.
Products – the new substance(s) that are formed during the chemical changes.
CHEMICAL EQUATION indicates the reactants and products of a reaction.
Objectives:
To identify seven elements that occur naturally as diatomic molecules, H2, N2, O2, F2, Cl2, Br2, I2. [HOBrFINCL twins or BrINClHOF brothers]
To write a chemical equation from the description of a chemical reaction.
REACTANTS  PRODUCTS

12. 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

13. 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

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

15. Visualizing a Chemical Reaction2
Na Cl NaCl 2

16. 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

17. 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?
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
Determine whether the following equation is balanced.
2 Na + H2O  2 NaOH + H2
2 Na H2O  2 NaOH + H2

18. 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.

19. 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?
Is this balanced?
NO(g) + ½ O2(g)  NO2(g)
Is this OK?

20. 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.
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).

21. Guidelines for Balancing Chemical Equations
1) polyatomic ions first ?
2) even / odd
(make all even)
3) H2O Mg(OH)2 2
H-OH vs.
4) single elements last
Example: need 13 oxygen atoms 13 2
“ ”
Multiply by O2 = 13
Method for balancing chemical equations
1. Identify the most complex substance.
2. Beginning with that substance, choose an element that appears in only one reactant and one product. Adjust the coefficients to obtain the same number of atoms of this element on both sides.
3. Balance polyatomic ions (if present) as a unit.
4. Balance the remaining atoms, usually ending with the least- complex substance and using fractional coefficients if necessary. If a fractional coefficient is used, multiply both sides of the equation by the denominator to obtain whole numbers for the coefficients.
5. Count the numbers of atoms of each kind on both sides of the equation to be sure that the chemical equation is balanced. 13 2
3X O Y Z
3X O Y Z 13 2 2
6X O Y Z

22. (NH4)3PO4 + Mg(OH)2  Mg3(PO4)2 3 + 6 NH4OH? 2
(NH4)3PO Mg(OH)2  Mg3(PO4)2 3 + 6
NH4OH
ammonium phosphate
magnesium hydroxide
magnesium phosphate
ammonium hydroxide
NH41+
OH1-
Now you try… 2
AlCl Li2CO  Al2(CO3) LiCl 3 6

23. Write a balanced equation for the reaction between chlorine
and sodium bromide to produce bromine and sodium chloride.
1) Write a word equation for the reaction.
chlorine sodium bromide  bromine + sodium chloride
2) Write the correct formulas for all reactants and products.
Cl NaBr  Br NaCl
3) Determine the coefficients that make the equation balance.
Cl NaBr  Br NaCl

24. Write the balanced equation for the reaction between aluminum sulfate and calcium chloride to form a white precipitate of calcium sulfate.
1) Write a word equation for the reaction. ? ?
aluminum sulfate + calcium chloride  calcium sulfate
+ aluminum chloride
2) Write the correct formulas for all reactants and products.
Al2(SO4) CaCl  CaSO AlCl3
3) Determine the coefficients that make the equation balance.
Al2(SO4) CaCl  CaSO AlCl3

25. CH4 + 2 O2  CO2 + 2 H2O Reactants Products 1 C atom 1 C atom
4 H atoms H atoms
4 O atoms O atoms

26. Reactants  Products + C(s) + O2(g) CO2(g) + H2(g) + O2(g) H2O (l) 2 2
carbon oxygen carbon dioxide
Reactants Product
1 carbon atom carbon atom
2 oxygen atoms oxygen atoms
catalyst – speeds up reaction + Pt
H2(g) O2(g) H2O (l)
hydrogen oxygen water 2 Pt 2
Reactants Product
4 hydrogen atoms hydrogen atoms
2 oxygen atoms oxygen atoms
Reactants Product
2 hydrogen atoms hydrogen atoms
2 oxygen atoms oxygen atoms
Reactants Product
2 hydrogen atoms hydrogen atoms
2 oxygen atoms oxygen atoms Un
balanced

27. Showing Phases in Chemical Equations
H2O(s) H2O(l) H2O(g)
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)

28. 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)

29. 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 D
2 atm
pressure
0 oC
MnO2

30. Types of Chemical Reactions
Synthesis (Combination) reaction
A B  AB
Decomposition reaction
AB  A + B
ASingle-replacement reaction
A BC  AC + B
element
compound
compound
element
BDouble-replacement reaction
AB CD  AD + CB
compound
compound
compound
compound
Neutralization reaction
HX BOH  BX + HOH
Objective:
To classify a chemical reaction as one of the following types: combination (synthesis), decomposition, single replacement, double replacement, or neutralization.
acid
base
salt
water
CH O2  CO2 + H2O
Combustion reaction (of a hydrocarbon)
Polymerization
Polymer = monomer + monomer + …
Ause activity series to predict
Bdriving force…water, gas, or precipitate

31. Types of Chemical Reactions
Synthesis (Combination) reaction
A B  AB
Decomposition reaction
AB  A + B
ASingle-replacement reaction
A BC  AC + B
BDouble-replacement reaction
AB CD  AD + CB
Neutralization reaction
HX BOH  BX + HOH
CH O2  CO2 + H2O
Objective:
To classify a chemical reaction as one of the following types: combination (synthesis), decomposition, single replacement, double replacement, or neutralization.
Combustion reaction (of a hydrocarbon)
Polymerization
Polymer = monomer + monomer + …
Ause activity series to predict
Bdriving force…water, gas, or precipitate

32. Nitrogen is in excess – or hydrogen is limiting reagent.
Chemical Equations
Chemical Equations
N2 (g) +
3 H2 (g)
2 NH3 (g) +
“Microscopic recipe”
1 molecule N2 +
3 molecules H2
2 molecules NH3
“Macroscopic recipe”
1 mol N2 +
3 mol H2
2 mol NH3
Experimental Conditions Reactants Products
Before reaction
1 mol N2 +
3 mol H2
2 mol NH3
2 molecules N2
3 molecules H2
0 molecules NH3
After reaction
1 molecules N2
0 molecules H2
2 molecules NH3
Nitrogen is in excess – or hydrogen is limiting reagent.

33. Synthesis Reaction Direct combination reaction (Synthesis)
2 Na Cl  NaCl Na Na Cl Cl  Cl Cl Na Na
General form: A B  AB
element or element or compound
compound compound

34. Synthesis Reaction Direct combination reaction (Synthesis)
2 Na Cl  NaCl Na Cl
Na+
Cl - Cl
Cl -
Na+ Na
General form: A B  AB
element or element or compound
compound compound

35. Formation of a solid: AgCl
AgNO3(aq) + KCl(aq)  KNO3 (aq) + AgCl(s)

36. 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)
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
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

37. Pb2+ Cl1- K1+ I1- Pb2+ Cl1- K1+ I1- Cl2 Pb I K KCl PbI2 + +
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
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)
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

38. + + Pb2+ Cl1- Pb2+ Cl1- K1+ K1+ I1- I1- I1- I1- Cl1- Cl1- K1+ K1+ I1-
lead(II) chloride potassium iodide
potassium chloride +
lead(II) iodide
Pb2+
Cl1-
K1+
I1-
Pb2+
Cl1-
K1+
I1-
Cl2 Pb
(aq) + I 2 K
(aq)
KCl
(aq) +
PbI2
(ppt)
Pb2+(aq) Cl1-(aq)
+ 2 K1+(aq) I1-(aq)
2 K1+(aq) Cl1-(aq)
+ Pb2+(aq) I1-(aq)
Pb2+
Cl1-
Pb2+
Cl1-
K1+
K1+
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
I1-
I1-
I1-
I1-
Cl1-
Cl1-
K1+
K1+
I1-
Pb2+
I1-
R E A C T A N T S P R O D U C T S
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
R E A C T A N T S P R O D U C T S

39. Ba2+ Ba2+ H1+ H1+ H1+ H1+ Ba2+ Double Replacement Reaction
aqueous barium nitrate reacts with sulfuric acid [H2SO4(aq)] to yield a barium sulfate precipitate and nitric acid [HNO3(aq)]
barium nitrate +
sulfuric acid
barium sulfate +
nitric acid
Ba NO31-
H SO42-
Ba SO42-
H NO31-
Ba(NO3)2
(aq) +
H2SO4
(aq)
BaSO4 + 2
HNO3
Ba(NO3)2(aq) H2SO4(aq) BaSO4 (ppt) HNO3(aq)
Ba2+(aq) NO31-(aq)
+ 2 H1+(aq) + SO42-(aq)
Ba2+(aq) + SO42-(aq)
+ 2 H1+(aq) NO31-(aq)
Ba2+
NO31-
Ba2+
NO31-
H1+
H1+
SO42-
SO42-
NO31-
NO31-
H1+
H1+
Ba2+
SO42-
R E A C T A N T S P R O D U C T S

40. 2+ 1- 1- 1+ 1+ 2- 1- 1- 1+ 1+ 2+ 2- barium nitrate + sulfuric acid
aqueous barium nitrate reacts with sulfuric acid [H2SO4(aq)] to yield a barium sulfate precipitate and nitric acid [HNO3(aq)]
barium nitrate +
sulfuric acid
barium sulfate +
nitric acid
Ba(NO3)2(aq) H2SO4(aq) BaSO4 (ppt) HNO3(aq)
Ba2+(aq) NO31-(aq)
+ 2 H1+(aq) + SO42-(aq)
Ba2+(aq) + SO42-(aq)
+ 2 H1+(aq) NO31-(aq) 2+ 1- 1- 1+ 1+ 2- 1- 1- 1+ 1+ 2+ 2-
R E A C T A N T S P R O D U C T S

41. Ca2+ Ca2+ H1+ H1+ H1+ H1+ Ca2+ Double Replacement Reaction
aqueous calcium nitrate reacts with sulfuric acid [H2SO4(aq)] to yield a calcium sulfate precipitate and nitric acid [HNO3(aq)]
calcium nitrate +
sulfuric acid
calcium sulfate +
nitric acid
Ca NO31-
H SO42-
Ca SO42-
H NO31-
Ca(NO3)2
(aq) +
H2SO4
(aq)
CaSO4 + 2
HNO3
Ca(NO3)2(aq) H2SO4(aq) CaSO4 (ppt) HNO3(aq)
Ca2+(aq) NO31-(aq)
+ 2 H1+(aq) + SO42-(aq)
Ca2+(aq) + SO42-(aq)
+ 2 H1+(aq) NO31-(aq)
Ca2+
NO31-
Ca2+
NO31-
H1+
H1+
SO42-
SO42-
NO31-
NO31-
H1+
H1+
Ca2+
SO42-
R E A C T A N T S P R O D U C T S

42. 2+ 1- 1- 1+ 1+ 2- 1- 1- 1+ 1+ 2+ 2- calcium nitrate + sulfuric acid
aqueous calcium nitrate reacts with sulfuric acid [H2SO4(aq)] to yield a calcium sulfate precipitate and nitric acid [HNO3(aq)]
calcium nitrate +
sulfuric acid
barium sulfate +
nitric acid
Ca(NO3)2(aq) H2SO4(aq) CaSO4 (ppt) HNO3(aq)
Ca2+(aq) NO31-(aq)
+ 2 H1+(aq) + SO42-(aq)
Ca2+(aq) + SO42-(aq)
+ 2 H1+(aq) NO31-(aq) 2+ 1- 1- 1+ 1+ 2- 1- 1- 1+ 1+ 2+ 2-
R E A C T A N T S P R O D U C T S

43. Na1+ Al3+ Al3+ Na1+ Na1+ Na1+ Na1+ Na1+ Al3+
Double Replacement Reaction
aqueous aluminum phosphate reacts with sodium hydroxide to yield a aluminum hydroxide precipitate and sodium phosphate
aluminum phosphate +
sodium hydroxide
aluminum hydroxide +
sodium phosphate
Al PO43-
Na OH1-
Al OH1-
Na PO43-
AlPO4
(aq) + 3
NaOH
(aq)
Al(OH)3 +
Na3PO4
AlPO4(aq) NaOH(aq) Al(OH)3(ppt) Na3PO4(aq)
Al3+(aq) + PO43-(aq)
+ 3 Na1+(aq) OH1-(aq)
Al3+(aq) OH1-(aq)
+ 3 Na1+(aq) + PO43-(aq)
OH1-
Na1+
Al3+
Al3+
Na1+
OH1-
Na1+
OH1-
OH1-
OH1-
PO43-
PO43-
OH1-
OH1-
Na1+
Na1+
Na1+
OH1-
Al3+
OH1-
R E A C T A N T S P R O D U C T S

44. Double Replacement Reaction
aqueous aluminum phosphate reacts with sodium hydroxide to yield a aluminum hydroxide precipitate and sodium phosphate
aluminum phosphate +
sodium hydroxide
aluminum hydroxide +
sodium phosphate
Al PO43-
Na OH1-
Al OH1-
Na PO43-
AlPO4
(aq) + 3
NaOH
(aq)
Al(OH)3 +
Na3PO4
AlPO4(aq) NaOH(aq) Al(OH)3(ppt) Na3PO4(aq)
Al3+(aq) + PO43-(aq)
+ 3 Na1+(aq) OH1-(aq)
Al3+(aq) OH1-(aq)
+ 3 Na1+(aq) + PO43-(aq) 1- 1+ 3+ 3+ 1+ 1- 1+ 1- 1- 1- 3- 1- 1- 1+ 1+ 1- 3+ 1-
R E A C T A N T S P R O D U C T S

45. Decomposition Reaction
2 H2O +
2 H2 O2 H H O O H + H O O H
General form: AB A + B
compound
two or more elements
or compounds

46. Single and Double Replacement Reactions
Single-replacement reaction
Mg CuSO4  MgSO Cu
General form:
A BC  AC B
Double-replacement reaction
CaCO HCl  CaCl H2CO3
General form:
AB CD  AD CB

47. Potassium reacts with Water
P O W !

48. Double Replacement Reaction
K2CO3 (aq)
Potassium carbonate +
BaCl2 (aq)
Barium chloride
2 KCl (aq)
Potassium chloride +
BaCO3 (s)
Barium carbonate

49. Synthesis Reactions Photosynthesis 6 CO2 + H2O C6H12O6 + O2 6 6
Formation of water 2
H O H2O 2
Formation of salt
A photomicrograph of common table salt © Carl J. Bowser, Department of Geology and Geophysics, University of Wisconsin, Madison 2
Na Cl NaCl 2
General Form
A B C

50. Decomposition Reactions
Hydrogen Peroxide 2
H2O H2O O2 2
Electrolysis of water
H2O H O2
electricity 2 2
Nitrogen triiodide 2
NI N I2 3
General Form
AB A B

51. Predict if these reactions will occur3
Mg AlCl3 2 2
Al MgCl2 3
Can magnesium replace aluminum?
YES, magnesium is more reactive than aluminum.
Activity Series
Al MgCl2
No reaction
Can aluminum replace magnesium?
NO, aluminum is less reactive than magnesium.
Therefore, no reaction will occur.
Activity Series
Order of reactants
DOES NOT
determine how
they react.
MgCl Al
No reaction
The question we must ask is can the single element replace its counterpart?
metal replaces metal or nonmetal replaces nonmetal.

52. Single-Replacement Reactions
Activity Series Li Rb K Ba Ca Na Mg Al Mn Zn Cr Fe Ni Sn Pb H2 Cu Hg Ag Pt Au
“Magic blue-earth”
Fe CuCl2
FeCl Cu
Can Fe replace Cu?
Yes
Zinc in nitric acid F2
Cl2
Br2 I2
Zn HNO3
Zn(NO3) H2 2
Can Zn replace H?
Yes
NO REACTION
MgBr Cl2
MgCl Br2
Can Br replace Cl? No
General Form
A BC AC B

53. KOH(aq) + HNO3(aq) KNO3(aq) + H2O ?
How would you prepare potassium nitrate
(using a double replacement reaction)?
potassium nitrate
formation of water
is a driving force. K K OH
KOH HNO KNO H2O + H H
NO3
KNO3 +
H2O
_________
_________
_________
Ca(NO3)2
Both potassium nitrate and
calcium chloride are soluble
(no driving force – no reaction!) 2
KOH +
Ca(NO3)2 2
KNO3 +
Ca(OH)2
Combine a potassium hydroxide solution with nitric acid
to yield soluble potassium nitrate.
KOH(aq) HNO3(aq) KNO3(aq) +
H2O ?
The water could then be removed by distillation to recover solid potassium nitrate.

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

55. Summary of Classes of Reactions
Chemical reactions
Precipitation
reactions
Oxidation-Reduction
Reactions
Acid-Base
Reactions
Combustion
Reactions
Synthesis
reactions
Decomposition
reactions

56. IONIC BONDING: Formation of Magnesium ChlorideCl Cl Mg
Mg2+ Cl Cl
Loses 2e- Each gains 1e One magnesium ion Two chloride ions
Mg Cl1-
[(2+) (1-) = 0]
MgCl magnesium chloride