REACTIONS
Chapter 7 |1
NAME____________________________
PERIOD_________
Chapter 7 REACTIONS
LEGGETT APIB REACTIONS Intro 1 (11:25)
http://youtu.be/mvS8tbXIs5k
https://vimeo.com/71918599
I. Introduction
A. Expected Prior knowledge:





Balancing chemical reactions
Endothermic – requires energy, energy is a reactant, surroundings get cold
Exothermic – releases energy, energy is a product, surroundings get hot
Evidence of a chemical reaction: (1) gas evolved (visual signs or apparent loss of mass) (2) color change (3)
precipitate formed (4) heat absorbed or released (5) new odor emerges (6) emission of light
Law of Conservation of Matter – total mass at beginning = total mass at end
Oxidation Number – covered in OnBoard. I will be happy to review with you!
· Used to keep track of electrons
· Shows the general distribution of electrons NOT absolute charge!
· Oxidation numbers will typically fall in the range: ─4 to +8, and can include zero!
SPECIES
RULE
Uncombined elements in
natural state. Ex: Fe(s), O2(g), P(s)
OXIDATION NUMBER IS ZERO
Binary Ionic Compounds
Ex. Fe3+ = +3, S─2 = ─2
Metals in Compounds
Ex. FeCl2, Fe = +2
Fluorine
OXIDATION NUMBER = IONIC CHARGE
Hydrogen
Ex. NH3 H = +1, CaH2 H = ─1
Oxygen
Ex: Na2O O = ─2, NaO O = ─1
+1 EXCEPT WHEN WITH METALS
Covalent/molecular
FOLLOW THEIR IONIC CHARGE. Gr 1 = +1, Gr 2 = +2, Gr 3 = +3,
Zn2+, Ag+, Cd2+
ALWAYS ─1
─2 EXCEPT: PEROXIDES = ─1 (If Oxygen is with a Gr. 1 or Gr 2
element CALCULATE OXYGEN!
EXCEPT: OF2 = +2 (F must be ─, therefore O = +2)
ASSIGN THE MOST ELECTRONEGATIVE ELEMENT ITS MOST
NEGATIVE VALUE ACC. TO THE PERIODIC TABLE.
CALCULATE THE OTHER (Gr. 17 = ─1, Gr. 16 = ─2, Gr. 15 = ─3)
The sum of oxidation numbers in a neutral compound is zero. CaCl 2: (+2) +
2(-1) = 0
The sum of oxidation numbers for a polyatomic ion equals the charge on the
polyatomic ion. PO4-3: (+5) + 4(-2) = -3
B. What is a chemical reaction?
A chemical change can be distinguished from a physical change because bonds, or ___________________
___________________, are broken and/or formed. New substances, with ___________________
___________________ properties are made. In a physical change (such as a phase change and dissolution),
___________________ ___________________, are broken.
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
Chapter 7 |2
There are some changes that are difficult to classify as chemical or physical. The dissolving of a salt is typically
considered a ___________________change. However, ionic bonds are broken, attractions between water and ion are
formed, and heat is often ___________________.
II. Broad classification of reactions: Reactions can be broadly sorted into two types:
A. Redox reactions: oxidation numbers of substances change. Electrons are lost (___________________) and
electrons are gained (___________________).
B. Not a redox reaction: no exchange of electrons occurs. These are typically faster than redox reactions.
III. Representations of reactions:
A. Molecular
B. Structural
+
3

2
+
2
C. Particle
D. NET IONIC EQUATIONS –
i.
Net ionic equations are streamlined to show only the species involved in the chemical change.
ii.
For ___________________reactions only.
iii.
We will ___________________soluble salts, strong acids, and strong bases.
iv.
In order to do these you need to re-memorize your strong acids, strong bases, and a couple of solubility rules.
LEGGETT APIB REACTIONS NET IONICS 2 (7:21)
http://youtu.be/c98XQ8Rhb5Q
http://vimeo.com/47796236
The charts below are provides for reference. You only need to memorize the rules for Group 1 salts,
ammonium, nitrate, and acetate.
SOLUBLE COMPOUNDS
EXCEPTIONS
All Group 1 salts
None
All ammonium (NH4+) salts
None
−
−
−
−
All NO3 , ClO3 , ClO4 , and C2H3O2 salts
None
All Cl−, Br−, I− salts
Ag+, Hg22+ (mercury (I)), Pb2+
All F− salts
Mg2+ Ca2+, Sr2+, Ba2and Pb2+
All salts of SO42−
Ca2+, Sr2+, Ba2+, Pb2+, Ag+, Hg22+
Group 1 & 2 hydroxides and NH4OH
All other hydroxides
Strong Bases (memorize): dissociate 100% in water. All hydroxides of group I and II* except beryllium and
magnesium.
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
Chapter 7 |3
* Completely dissociated in solutions of 0.01 M or less. These are insoluble bases which ionize 100%. The other five in the list can
easily make solutions of 1.0 M and are 100% dissociated at that concentration.
Strong Acids (memorize) - dissociate 100% in water
Type
Hydrogen halides (aq)
Oxyacids of halogens
Formula
HCl
HBr HI
HClO3
HClO4
HIO4
Sulfuric (1st H+ only!!) H2SO4  H+ + HSO4─
Nitric Acid
HNO3
There are three steps, although with practice you can skip one.
Complete
Formula
Complete
Ionic
Net Ionic
LEGGETT APIB REACTIONS NET IONICS 3 (6:37)
Spectator Ions:
http://youtu.be/OqTMyBf4yAc
http://vimeo.com/47796331
EXAMPLE: Aqueous solutions of lead (II) nitrate and potassium iodide are combined to form lead (II) iodide
and potassium nitrate.
Complete
Formula
Complete
Ionic
Net Ionic
Spectator Ions:
EXAMPLE: Chlorine gas is bubbled through a solution of potassium bromide to form bromine and potassium
chloride.
Complete
Formula
Complete
Ionic
Net Ionic
Spectator Ions:
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
LEGGETT APIB REACTIONS Double Repl 4(9:17)
Chapter 7 |4
http://youtu.be/RhqjMREUGEk
https://vimeo.com/71920087
IV. DOUBLE REPLACEMENT – NEVER A REDOX
A. How to Recognize: Two ionic AND/OR ACIDS AND/OR BASES compounds react
1. one or both will be soluble
2. one or both of the products will be a solid, a gas, or water
3. these are not redox reactions so oxidation numbers will remain unchanged.
B. Examples:
EXAMPLE: One Product: Solutions of silver nitrate and sodium chromate are mixed.
Complete
Formula
Complete
Ionic
Net Ionic
Spectator Ions:
EXAMPLE: Two Products: Sulfuric acid and barium acetate are mixed.
Complete Formula
Complete Ionic
Net Ionic
LEGGETT APIB REACTIONS Single Repl 5(11:42)
SIs:
http://youtu.be/5UFcOJ1lyEU
https://vimeo.com/71921794
V. SINGLE REPLACEMENT – ALWAYS A REDOX
A. How to recognize:
1. metal plus an ionic compound
2. Active metal plus water
3. Active metal plus acid
4. halogen plus an ionic halide
5. these are a subset of redox (typically simpler)
B. Don’t forget:
1. Diatomics: I Bring Clay For Our New House
2. Metals that oxidize to their higher oxidation state: As Snoopy Fell Huge Cups Cracked. All the
rest oxidize to their lower oxidation state.
3. An activity series shows which metals prefer to be oxidized. Reading an activity series is a lower
order thinking skill (PreAP/IB chem). Interpreting the results of reactions is a higher order thinking
skill (AP/IB chem).
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
Chapter 7 |5
EXAMPLE: The following reactions are thermodynamically favorable. Rank the metals from least active to most
active.
i.
ii.
iii.
When a copper penny is dropped into concentrated nitric acid, the solution temperature increases and a
orange/brown gas is formed. The copper penny disappears. Hydrochloric acid does not result in a chemical
reaction.
Calcium pellets are added to water. A gas bubbles up and litmus paper turns blue. When a lit splint is placed
into a container of the gas, a popping sound is heard.
When hydrochloric acid is poured over mossy zinc, hydrogen gas is collects. When mossy zinc is added to water,
no reaction occurs.
LEGGETT APIB REACTIONS Single Repl 6(9:19)
http://youtu.be/T0uAqaGWW_g
C. Types:
1. Metal plus an ionic compound.
EXAMPLE: Magnesium shavings are added to a solution of iron (II) chloride:
COMPLETE FORMULA
COMPLETE IONIC
NET IONIC
Fe becomes solid: LOSE THE CHARGE!
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
http://vimeo.com/71923302
REACTIONS
Chapter 7 |6
2. Active metal plus water
EXAMPLE: A piece of sodium add carefully dropped into water:
COMPLETE
FORMULA
COMPLETE
IONIC
NET IONIC
SI:
3. Active metal plus acid
EXAMPLE: A piece of mossy zinc is added to hydrochloric acid:
COMPLETE FORMULA
COMPLETE IONIC
NET IONIC
SI:
4. Halogen plus and ionic halide
EXAMPLE: Chlorine gas is bubbled through a solution of chromium(II) iodide:
COMPLETE FORMULA
COMPLETE IONIC
NET IONIC
LEGGETT APIB REACTIONS Synthesis Decomp 7
(6:11)
SI:
http://youtu.be/N-9JKeVsodg
https://vimeo.com/71924436
VI. COMBINATION/SYNTHESIS/ADDITION AND DECOMPOSITION
A. Basics
1.
2.
3.
4.
These are typically the opposite of one another.
You should be able to predict elements forming compounds and vice versa
More complicated reactions will have data to help determine products.
Since these typically are not performed in an aqueous solution, we will not write net ionic equation (the
formation of ions requires water)
5. Decomposition is typically when single compound is heated (), electrolyzed, decomposed – often in the
presence of a catalyst such as MnO2. Heat, electricity, and catalysts are shown above the arrow in the
reaction.
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
Chapter 7 |7
B. Element + element ⇄ Compound – Always a redox
EXAMPLE: A stream of hot nitrogen flows over a piece of sodium:
Synthesis
Decomposition
C. Cmpd + Cmpd – not usually a redox – assign oxidation numbers to be sure!
EXAMPLE: Calcium oxide is exposed to a stream of carbon dioxide:
Synthesis
Decomposition
EXAMPLE: Carbon dioxide is bubble through water.
Synthesis
Decomposition
LEGGETT APIB REACTIONS Combustion 8(3:20)
VII.
http://youtu.be/5YNd2ejxzII
http://vimeo.com/71925324
COMBUSTION – ALWAYS A REDOX
A. How to recognize:
1. adding oxygen to a compound or element
2. Look for words such as “burned”, “undergoes combustion”. NOTE: You need to supply the oxygen because it
will not be explicitly given!
B. Examples:
EXAMPLE: Propane is combusted in excess oxygen:
EXAMPLE: Magnesium sulfide is burned in air:
LEGGETT APIB REACTIONS Acid Base 9(7:08)
VIII.
http://youtu.be/Yr5e4rF4T0I
ACID BASE NEUTRALIZATION – NOT A REDOX
A. How to Recognize:
1. Look for an acid plus a base.
2. This is really a subset of double replacement with products typically being a salt and water.
3. If the acid is polyprotic, the product may still be an acid.
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
B. Types:
Chapter 7 |8
1. Fully Neutralized
Example: Hydrogen sulfide gas is bubbled through a solution of excess potassium hydroxide.
Complete
Formula
Complete Ionic
Net Ionic
Spectator
Ions:
2. Partially Neutralized
EXAMPLE: 25 mL of 0.100 M solutions of sodium hydroxide and carbonic acid are mixed. A few drops of
phenolphthalein are added and the solution remains colorless.
Complete
Formula
Complete Ionic
Net Ionic
Spectator Ions:
LEGGETT APIB REACTIONS Complex Ion 10 (6:25)
IX.
http://youtu.be/mi202krihRk
http://vimeo.com/71926504
COMPLEX IONS/COORDINATION COMPOUNDS
A. How to recognize: Transition metal or aluminum with ammonia, hydroxide, cyanide,
B. Definitions:
1. Coordinate Covalent Bond: A covalent bond in which one of the bond participants supplies both of the electrons.
2. Ligand: the substance that donates two electrons to form the bond.
3. Complex ion: Cation or anion substance that forms
4. Coordination complex: Complex ion with a counter ion to balance charge to form a neutral complex
C. Examples:
EXAMPLE: The copper(II) ion reacts with four ammonia molecules to form a complex ion.
EXAMPLE: Write the net ionic reaction for the formation of Al(OH)63- complex ion from potassium hydroxide and solid
aluminum hydroxide.
Complete
Formula
Complete Ionic
Net Ionic
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
Spectator Ions:
REACTIONS
LEGGETT APIB ELECTROCHEM 14 (8:32)
Chapter 7 |9
http://youtu.be/z5owzAOeDjU
http://vimeo.com/63623366
I deleted the first half of this video for the new curriculum, but it is a good review of oxidation numbers!
Balancing Redox – atoms, electrons and charge must be balanced!
A. ½ rxn method
1. Write down the chemical equation.
2. Determine all oxidation numbers.
3. Determine the change in electrons or write down balanced ½ rxns.
4. Find a common multiple for the number of electrons in each ½ rxn such that: # e-’s gained = # e-’s lost
5. Move coefficients from the ½ rxn to the complete rxn.
6. Complete the balancing process for the remaining elements.
NOTE: If not all of an element is oxidized or reduced you may not be able to use the coefficient.
EXAMPLE For the following reactions identify what is oxidized, what is reduced, the oxidizing agent, and the
reducing agent. Balance the following redox equations. All steps must be shown
a) ____ H2S + ____ O2
LEGGETT APIB ELECTROCHEM 15
→
____ SO2 + ____ H2O
http://youtu.be/Uo9jYlUzRvI
b) ____ HMnO4 + ____ HCl →
https://vimeo.com/63623365
____ MnCl2 + ____ Cl2 +____ H2O
B. Balancing in Acidic Soln:
1. Balance the oxygens with water.
2. Balance the hydrogens with H+.
3. Cancel of necessary
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX
REACTIONS
EXAMPLE (acidic)
(acidic)
______ Cu + ______ NO3
______Cr2O72
—
+ ______
─
→
C h a p t e r 7 | 10
______ Cu + ______ NO2
+2
—
Cl → ______ Cr3+ + ______ Cl2
C. Balancing in Basic Soln:
(basic)
(basic)
─
─
______Br2(l) → ______ Br (aq) + ______ BrO3 (aq)
______MnO4─ + ______ IO3─ → ______ MnO2 + ______ IO4─
©2015 Allen ISD, Dena K. Leggett, Ph.D., Allen High School, Allen, TX