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