wednesday, sept. 4 th : “a” day thursday, sept. 5 th : “b” day agenda homework...
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Wednesday, Sept. 4th: “A” DayThursday, Sept. 5th: “B” Day
AgendaHomework questions/collect (pg. 274: 1-6 & WS)Quiz Sec. 8.2: “Balancing Chemical Equations”Sec. 8.3, Day 1: “Classifying Chemical Reactions”
Combustion, synthesis, decompositionHomework:
1. Sec. 8.3 review, pg. 285: #1-4, 8b,c,f, 10a,b,e,f, 122. Practice pg. 279: #1-43. Concept Review: “Classifying Chemical Reactions”
1-3, 6-9 only
Homework QuestionsPg. 274: #1-6
“Chemical Formulas and Equations” Worksheet
“Writing Chemical Formulas” Worksheet
Section 8.2 Quiz“Balancing Chemical Equations”
As always, you may use your guided notes and book on the quiz…
May the FORCEbe with you!
Diatomic Elements
Before we begin this section, remember that the following elements are diatomic and exist as molecules…
H2, O2, N2, F2, Cl2, Br2, I2
Sec. 8.3“Classifying Chemical Reactions”
By classifying chemical reactions into several types, the products that are likely to form are more easily predicted.
Also, reactions of each type follow certain patterns, which will make balancing them easier.
The 5 types of reactions that are covered in this section are………….
5 Types of Chemical Reactions
1. Combustion2. Synthesis (sometimes called combination)3. Decomposition4. Single Displacement 5. Double Displacement
Combustion ReactionsCombustion reaction: the oxidation reaction
of an organic compound, in which heat is released.The reaction of a carbon-based compound
with oxygen.Products are always carbon dioxide, CO2,
and water vapor, H2O.
C3H8 + 5 O2 3 CO2 + 4 H2O (Complete combustion of propane, C3H8)
Combustion ReactionsIf there’s not enough oxygen present, the
combustion reaction is INCOMPLETE.Carbon monoxide, CO, and unburned carbon (soot)
are produced along with CO2 and H2O.
2 C3H8 + 7 O2 2 C + 2 CO + 2 CO2 + 8 H2O(Incomplete combustion of propane, C3H8)
**Combustion reactions can be tricky to balance**
Synthesis ReactionSynthesis Reaction: a reaction in which two or
more substances combine to form a new compound. (Occasionally more than 1 product)A single compound forms from 2 or more
reactants.If the reaction only has 1 product, it’s a
synthesis reaction.Many times, the reactants are 2 elements or 2
small compounds.Sometimes called “combination” reactions
Synthesis ReactionsTwo Elements Form a Binary
CompoundIf the reactants are 2 elements, the only way they
can react is to form a binary compound, which is composed of 2 elements.
When a metal reacts with a non-metal, an ionic compound forms and the charges on the ions can be used to predict the formula for the compound that will be formed.
2 Na + Cl2 2 NaCl(synthesis of sodium chloride)
Synthesis ReactionsTwo Elements Form a Binary CompoundWhen 2 non-metals react, often more than one
compound could form, so predicting the products of these reactions is not always easy.
C + O2 CO2
2 C + O2 2 CO
You will probably need more information to predict the products of these reactions and to balance them correctly.
Synthesis Reactions2 Compounds Form a Ternary Compound
Two compounds can combine to form a ternary compound, a compound composed of 3 elements.
CaO(s) + H2O(l) Ca(OH)2 (s)**(Group 1 or 2 metal oxides react w/water
to form a metal hydroxide)**
CO2(g) + H2O(l) H2CO3 (aq)(Some oxides of non-metals can combine
w/water to produce acids)
Decomposition ReactionsDecomposition Reaction: a reaction in which
a single compound breaks down to form two or more simpler substances.Decomposition reactions are the OPPOSITE
of synthesis reactions - only 1 reactantA single compound breaks down, often
with the input of energy, into 2 or more elements or simpler compounds
Decomposition Reactions
If your reactant is a binary compound, then the products will most likely be the 2 elements that make up the compound.
2 H2O(l) electricity O2(g) + 2 H2 (g)(decomposition of water)
Decomposition ReactionsCompounds made up of 3 or more elements usually
don’t decompose into those elements.
CaCO3(s) heat CaO(s) + CO2(g)
**(A metal carbonate decomposes to form a metal oxide and carbon dioxide)**
**A compound with a polyatomic ion, like CO3, will likely break down to a simpler
substance, like CO2**
Sample Problem D, Pg. 279Predicting Products
Predict the product(s) and write a balanced equation for the reaction of potassium with chlorine.
Reactants: Potassium, K, and chlorine, Cl2
Because the reactants are 2 elements, the reaction is most likely a synthesis reaction.
K will LOSE 1 electron to form K+ and Cl will GAIN an electron to form Cl- so the formula for the product will be KCl. K + Cl2 KCl
Lastly, balance the equation:
2 K + Cl2 2 KCl
Additional ExamplePredict the product(s) and write a balanced
equation for the reaction of pentane, C5H12, with oxygen.
Reactants: pentane, C5H12, and oxygen, O2
Because the reactants are a hydrocarbon and oxygen, we have a combustion reaction.
Products: CO2 and H2O
C5H12 + O2 CO2 + H2OLastly, balance the equation:
C5H12 + 8 O2 5 CO2 + 6 H2O
Additional ExamplePredict the product(s) and write a balanced
equation for the decomposition of sodium chloride, NaCl.
Reactant: Sodium chloride, NaClBecause we have 1 reactant, the reaction is a
decomposition reaction.
NaCl Na + Cl2
Lastly, balance the equation:
2 NaCl 2 Na + Cl2
Homework
Sec. 8.3 review, pg 285: 1-4, 8b,c,f, 10a,b,e,f, 12Practice box, pg. 279: #1-4Concept Review, “Classifying Chemical
Reactions”: 1-3, 6-9
We will finish section 8.3 next time…
High School Open House: Tonight, 6:30 -8:00 pm