1. stoichiometry

2. Chemical Equations

3. Balancing equations
The Eq. must represent the
known facts.
2. The Eq. must contain the correct formulas for reactants and products.
3. The law of conservation of mass must be followed.
4. Balance atoms that appear once 1st.
5. Treat polyatomics as one unit if they appear on both sides the same way.

4. 6. Balance other elements.
7. Balance H
8. Balance O last!!
*NEVER CHANGE A SUBSCRIPT

5. Chemical Reactions and Equations: Basic Concepts
Topic 8
Balancing an Equation
The balanced equation tells us that when carbon and oxygen react, one unit of oxygen react with each molecule of carbon to form one unit of carbon dioxide

6. Conservation of Mass and Balancing Equations
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7. Example
Write and balance the reaction between sodium hydroxide and calcium bromide to give calcium hydroxide and sodium bromide NaOH + CaBr2  Ca(OH)2 + NaBr
2 NaOH + CaBr2  Ca(OH)2 + 2NaBr

9. Here are some more to balance:
a) 2KNO3  2KNO2 + O2
b) 2Pb(NO3)2  2PbO + 4NO2 + O2
c) P4 + 6I2  4PI3
d) 3MgO + 2H3PO4  Mg3(PO4)2 + 3H2O
e) Br2 + 2KI  I2 + 2KBr
f) Ca(OH)2 + 2HNO3  Ca(NO3)2 + 2H2O
g) Bi2O3 + 3H2  2Bi + 3H2O
h) 3Fe + 2O2  Fe3O4
i) 2CaO + 5C  2CaC2 + CO2

10. Classification of Reactions
There are 5 major classifications of reactions:
Synthesis A + B → AB
Decomposition AB → A + B
Combustion Hydrocarbon + O2 → CO2 + H2O
Single Replacement AB + C → AC + B
Double Replacement AB + CD → AD + CB

12. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
In one type of reaction, two substances—either elements or compounds—combine to form a compound.
Whenever two or more substances combine to form a single product, the reaction is called a synthesis reaction.

13. Chemical Reactions and Equations: Basic Concepts
Topic 8
A Synthesis Reaction
When iron rusts, iron metal and oxygen gas combine to form one new substance, iron(III) oxide.
The balanced equation for this synthesis reaction shows that there is more than one reactant but only one product.

14. A Synthesis Reaction Topic 8
Chemical Reactions and Equations: Basic Concepts
Topic 8
A Synthesis Reaction

15. Synthesis (Combination)
Synthesis – when 2 or more substances react to produce 1 product
Of the form: A + B  AB
Examples:
2 Fe + 3 Cl2  2 FeCl3
2 Na + Cl2  2NaCl
CaO + H2O  Ca(OH)2
2Mg + O2  2MgO

16. Synthesis # 1
Metal oxide + nonmetal oxide  metal oxyanion a salt (Not Redox)
No Redox simply means that the oxidation numbers of the elements stays the same
Oxyanion = a polyatomic ion with oxygen

17. Synthesis # 1 Example
Sulfur dioxide gas is passed over solid calcium oxide
SO2 + CaO 
We know that we have to get a metal oxyanion.
So we either get CaSO4 or CaSO3
We need to check the oxidation states on sulfur to see which one is the same.

18. Synthesis # 1 Example In SO2, the oxidation number of O is -2
So the oxidation number of S must be +4
Our product choices are CaSO3 or CaSO4
In CaSO3…S has an oxidation # of +4
In CaSO4…S has an oxidation # of +6
Therefore the product must be CaSO3
SO2 + CaO  CaSO3

19. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
In a decomposition reaction, a compound breaks down into two or more simpler substances.
The compound may break down into individual elements, such as when mercury(II) oxide decomposes into mercury and oxygen.

20. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
The products may be an element and a compound, such as when hydrogen peroxide decomposes into water and oxygen.
The compound may break down into simpler compounds.

21. A Decomposition Reaction
Chemical Reactions and Equations: Basic Concepts
Topic 8
A Decomposition Reaction
When ammonium nitrate is heated to a high temperature, it explosively breaks down into dinitrogen monoxide and water.
The decomposition reaction taking place is represented by a balanced equation that shows one reactant and more than one product.

22. A Decomposition Reaction
Chemical Reactions and Equations: Basic Concepts
Topic 8
A Decomposition Reaction

23. Decomposition
Decomposition – when a single compound breaks down into 2 or more compounds
Of the form: AB  A + B
Note that this is the exact opposite of synthesis
Examples:
2 Na3N  6 Na + N2
NH4NO3  N2O + 2H2O
2H2O  2 H2 + O2

24. Decomposition Synthesis Decomposition Redox Non Redox
Metal + Nonmetal  salt
Salt  Metal + Nonmetal
Non Redox
Metal oxide + H2O  base
base  Metal oxide + H2O
Nonmetal oxide + H2O  acid
acid Nonmetal oxide + H2O
Metal oxide + Nonmetal oxide  salt
salt  Metal oxide + Nonmetal oxide

25. More Decomposition Metal chlorates  metal chloride + O2
(NH4)2CO3  2NH3 + H2O + CO2
2H2O2  2H2O + O2
If you get any of these products…they decompose…
NH4OH  NH3 + H2O
H2CO3  CO2 + H2O
H2SO3  SO2 + H2O
HNO2  NO + NO2 + H2O

26. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
A combustion reaction is one in which a substance rapidly combines with oxygen to form one or more oxides.
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27. Chemical Reactions and Equations: Basic Concepts
Topic 8
Combustion
When welding is done with an acetylene torch, acetylene combines with oxygen to form carbon dioxide and water.
This combustion reaction is exothermic, and enough energy is released to melt metal.

28. Chemical Reactions and Equations: Basic Concepts
Topic 8
Combustion

29. Combustion
Combustion – when O2 combines with a hydrocarbon to form CO2 and H2O
Of the form: hydrocarbon + O2  CO2 + H2O
For example:
CH4 + 2 O2  CO2 + 2H2O
2CH3OH + 3O2  2CO2 + 4H2O

30. Combustion Hydrocarbon + O2 CO2+ H2O (No ions) Combustion of methane
CH4 + O2 CO2+ H2O
CH4 + 2O2 CO2+ 2H2O

32. When Balancing Combustion Reactions
Put a two in front of the hydrocarbon to start.
Balance them in the order C, H, O
Make sure your answer is in the lowest whole number ratio

33. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
In a single-displacement reaction, one element takes the place of another in a compound.
The element can replace the first part of a compound, or it can replace the last part of a compound.

34. Chemical Reactions and Equations: Basic Concepts
Topic 8
Single Displacement
If an iron nail is placed into an aqueous solution of copper(II) sulfate, the iron displaces the copper ions in solution, and copper metal forms on the nail.

35. Single Displacement Topic 8
Chemical Reactions and Equations: Basic Concepts
Topic 8
Single Displacement

36. Single Replacement
Single Replacement – when the atoms of one element replace the atoms of another element in a compound
Of the form : A + BX  B + AX
For example:
2 Li + 2H2O  2 LiOH + H2
Cu + 2AgNO3  2 Ag + Cu(NO3)2

37. Page 286 TABLE 3 in your text book
Activity Series
Page 286 TABLE 3 in your text book

38. Single Replacement Reactions
In order for a single replacement reaction to occur, the element that is by itself must be strong enough to push the other element out of the way.
The activity series show you the relative pushing power of the elements.
In order for the reaction to occur, the lone element must be above the element in the compound
Otherwise…NO REACTION  NR

39. Single Replacement Reactions
You need to know which chart you are to look at…metals or halogens.
A metal can replace another metal
A halogen can replace another halogen

40. Will these reactions occur?
Will the following reaction occur? If so, complete and balance the reaction.
Ag + Cu(NO3)2 
Ag + Cu(NO3)2 NR
No reaction because Ag is below Cu in the Activity series of metals

41. Will these reactions occur?
Will the following reaction occur? If so, complete and balance the reaction.
Mg + AlCl3 
3Mg + 2AlCl3 3MgCl2 + 2 Al
The reaction WILL occur because Mg is above Al in the activity series

42. Will these reactions occur?
Will the following reaction occur? If so, complete and balance the reaction.
Br2 + MgCl2 
Br2 + MgCl2  NR
This reaction will NOT occur because Br is not above Cl in the activity series of halogens

43. Double Replacement
Double Replacement – a reaction involving the exchange of ions between 2 compounds
Of the form: AX + BY  BX + AY

44. Major Classes of Reactions
Chemical Reactions and Equations: Basic Concepts
Topic 8
Major Classes of Reactions
In double-displacement reactions, the positive portions of two ionic compounds are interchanged.
For a double-displacement reaction to take place, at least one of the products must be a precipitate or water.

45. Chemical Reactions and Equations: Basic Concepts
Topic 8
Double Displacement
When clear aqueous solutions of lead(II) nitrate and potassium iodine are mixed, a double-displacement reaction takes place and a yellow solid appears in the mixture.
This solid is lead(II) iodine, and it precipitates out because it is insoluble in water, unlike the two reactants and the other product.

46. Double Displacement Topic 8
Chemical Reactions and Equations: Basic Concepts
Topic 8
Double Displacement

47. Double Replacement (Metathesis)
Double Replacement – a reaction involving the exchange of ions between 2 compounds
Of the form: AX + BY  BX + AY
Examples:
Pb(NO3)2 + 2KI  PbI2 + 2KNO3
Na2CO3 + 2AgNO3  2NaNO3 + Ag2CO3

48. Double Replacement (Metathesis)
In order for a double replacement reaction to take place, one of 3 things must be formed:
Precipitate (solid)
Gas
Weak electrolyte – usually water

49. Precipitation Reactions
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50. Solubility Rules!!!

51. Double Replacement # 2 (Formation of a gas)
Formation of a gas (acid + sulfide, sulfite, carbonate, or bicarbonate…or ammonium salt + a strong base  NH3(g), H2O, and a salt)
Hydrobromic acid is added to a solution of potassium bicarbonate
HBr + KHCO3 
HBr + KHCO3  H2CO3 + KBr
H2CO3 ALWAYS breaks down into CO2 + H2O
HBr + KHCO3 CO2 + H2O + KBr
H+ + HCO3- CO2 + H2O

52. Double Replacement #4 (Acid Base neutralization)
Acid + base  salt + water
Hydrogen sulfide gas is bubbled through excess potassium hydroxide solution
H2S + 2KOH  2HOH + K2S
H2S + 2K+ + 2OH-  2H2O + 2K+ + S-2
H2S + 2OH-  2H2O + S-2

53. Proton Transfer Click in this box to enter notes.
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54. Ionic Equations

55. Equations
Molecular equations – show the complete chemical formulas. Does not indicate ionic character
Complete ionic equation – shows all ions. Actually how the particles exist in the solution

56. Steps for Writing Ionic Equations
Write the balances molecular equation (balanced chemical equation)
Break every thing down into its ions EXCEPT the solid, gas, or water (complete ionic equation)
Cross out everything that is the same on both sides (spectator ions)
Write what is left (net ionic equation)

57. Rules
When writing ionic equations, you must keep together the solid, gas, or water
Spectator ions – ions that appear on both sides of the equation. They have very little to do with the chemical reaction

58. Example
Write the balanced chemical equation, the complete ionic equation, and the net ionic equation for the reaction between lead (II) nitrate and potassium iodide. Solid potassium iodide will be formed.

59. Example Write the balanced chemical equation
Pb(NO3)2 + 2 KI  PbI2 + 2 KNO3
You MUST identify the solid, gas, or water
Pb(NO3)2 + 2 KI  PbI2 (s) + 2 KNO3
Balanced chemical equation

60. Example
Now break every thing except the solid, gas, or water into its ions
Remember ions are things with charges
Everything will be broken down into one positive charge and one negative charge

61. Example Pb(NO3)2 + 2 KI  PbI2 (s) + 2 KNO3 Complete ionic Equation

62. Example
Now cross out everything that is the same on both sides (spectator ions)
Pb+2 + 2NO K I -1  PbI2 (s) + 2K+1 + 2NO3-1
Now write what is left
Pb I -1  PbI2 (s)
Net ionic equation

63. Another Example
Write the balanced chemical equation, complete ionic equation, and net ionic equation for the reaction between calcium chloride and sodium carbonate. Solid calcium carbonate will be formed.

64. Another Example Balanced chemical equation
CaCl2 + Na2CO3  CaCO3 (s) + 2NaCl
Complete ionic equation
Ca+2 + 2Cl Na +1 + CO3 -2  CaCO3 (s) + 2Na Cl -1
Net Ionic Equation
Ca+2 + CO3 -2  CaCO3 (s)

65. What if water is formed?
Write the balanced chemical equation, complete ionic equation, and net ionic equation for the reaction between Calcium hydroxide and nitric acid

66. Example with water 2(OH) -1 + 2H+1  2 HOH Balanced chemical equation
Ca(OH)2 + 2 HNO3  Ca(NO3)2 + 2 HOH
Complete ionic equation
Ca+2 + 2(OH) H+1 + 2NO3 -1  Ca+2 + 2NO HOH
Net Ionic Equation
2(OH) H+1  2 HOH

67. Stoichiometry
Using the methods of stoichiometry, we can measure the amounts of substances involved in chemical reactions and relate them to one another.

68. Stoichiometry Rules 1. Balance the equation.
2. convert all units to moles
3. use a molar ratio from the balanced equation to compare what is given to what you want.
4. convert back from moles to the unit the question asks for.

69. Always no matter what unit you are given convert it to moles before you make a comparison.

70. Coefficients
Coefficients in a balanced chemical RXN can represent any of the following
1. moles
2. molecules of a compound
3. volume of a gas at STP. (22.7 L=1mol)
* they never represent mass.

71. Mole – Mole Relationship
4 Fe + 3O2  2Fe2O3
4 mol Fe / 3 mol O2
4 mol Fe / 2 mol Fe2O3
3mol O2 / 2 mol Fe2O3

72. Mole – Mole Relationship
How many moles of Fe2O3 will I form from 5.0 mol of Fe?
5.0 mole Fe x 2 mol Fe2O3
4 mol Fe
2.5 mol Fe2O3

73. The #’s in from if A & B MUST come from the balanced chemical equation
Conversion Factor # 3
# Moles A
# Moles B
The #’s in from if A & B MUST come from the balanced chemical equation

74. Mass – Mole Relationship
How many g of NaCl will be produced from 1.25 mol of chlorine gas reacting with sodium?
Write the reaction
Na + Cl2  NaCl
Balance the reaction
2Na + Cl2  2NaCl

75. Mass – Mole Relationship
Work the problem
1.25 mol Cl2 x 2 mol NaCl x g NaCl
1 mol Cl mol NaCl
146 g NaCl

76. Mass – Mass Relationships
Ammonium nitrate decomposes into dinitrogen monoxide gas and water. Determine that amount of water produced if 25.0 g of ammonium nitrate decomposes.
NH4NO3  N2O + H2O
NH4NO3  N2O + 2 H2O

77. Mass – Mass Relationships
25.0 g NH4NO3 x 1 mol NH4NO3 x 2 mol H2O x g H2O
80.04 g NH4NO mol NH4NO mol H2O
11.2 g H2O