BALANCING EQUATIONS &

CHEMICAL REACTIONS

Evidence of Chemical Change

Changes in Energy (E) Release of E as heat Release of E as light Production of sound Reduction or increase of

temperature Absorption or release of

electrical Energy

Formation of new substances

Formation of a gas Formation of a

precipitate Change in color Change in odor

Conservation of Mass

Law of Conservation of Mass In any physical or chemical reaction, mass

is neither created nor destroyed; it is conserved!

Reactants Products

Same number of atoms on both

sides of the equation!

Balancing Equations

In every balanced equationeach side of the equation

has the same number of atoms of each element

Important stuff!

Four abbreviations are used to indicate physical states of chemicals: shown as subscripts in the chemical equation

(s) = solid(l) = liquid(g) = gas(aq)= aqueous solution

(dissolved in water)

Symbols over the arrow indicate the conditions of the reaction

HeatPressureTemperatureCatalystReversible reaction

Balance this equation…

NaNO3 + CrCl3 NaCl + Cr(NO3)3

How would you “write” it?

Combination Reactionor Synthesis Reaction

Two or more simple substances react to form a more complicated one

A + B AB

Fe + S FeS

Combination Reactions

We can predict the products of ionic compounds by thinking about the charge!

Al (s) + O2 (g)

Cu (s) + S(s)

Are there 2 possible products to this reactionsHow would we “say” these equations?

Decomposition Reaction

A decomposition reaction is the opposite of a composition reaction - a complex molecule breaks down to make simpler ones.

AB A + B

2 H2O 2 H2 + O2

Decomposition Reactions

Harder to predict the products…always remember your diatomics.

Water is often a product!

HgO(s)

NH4NO3

Decomposition Reactions

HgO(s) 2HgO(s) 2Hg(l) + O2 (g)

NH4NO3 NH4NO3 N2O + 2H2O

The only way to really know is to do the reaction!!

Single Replacement

This is when one element trades places with another element in a compound.

A + BC AC + B

Mg + 2H2O Mg(OH)2 + H2

Single Replacement Reactions

Easy to predict the products. Look at the ions… remember that a cation has to bond to an anion!!

Don’t forget about diatomics!

Zn(s) + H2SO4(aq)

Na(s) + H2O

OOPS! Did we balance them?

Single Replacement Reactions

Zn(s) + H2SO4(aq) Zn(s) + H2SO4(aq) ZnSO4(aq) + H2(g)

Na(s) + H2O Na(s) + H+OH-

(l) 2Na(s)+ 2H+OH-

(l) 2NaOH + H2(g)

Single Replacement Reactions

Reactivity of a metal makes a difference!

If a metal is more reactive than the metal it is displacing a rxn will occur. If the metal is less reactive than the metal it is displacing, a rxn will not occur.

Metal Reactivity

Increases down a group

Decreases across a period

Brainiacs-- Metal Reactivity

Reactivity in Single Displacement

Cs + KMnO4 CsMnO4

Will this occur??

Na + KMnO4 NaMnO4 + KWill this occur?

Double Replacement Reaction

This is when the anions and cations of two different molecules switch places, forming two entirely different compounds

AB + CD AD + CB

Pb(NO3)2 + 2KI PbI2 + 2KNO3

Double Replacement Reactions

Generally take place between two ionic compounds in aqueous solution

Pb(NO3)2 + 2KI PbI2 + 2KNO3

Double Replacement Reactions

2NaCl + H2SO4

Double Replacement Reactions

Ca(OH)2(aq) + 2HCl(aq) )

Combustion Reactions

A combustion reaction is when oxygen combines with another compound or element producing energy.

When hydrocarbons (C?H?) combust, water, carbon dioxide and energy are produced.

C10H8 + 12 O2 10 CO2 + 4 H2O + Energy

Combustion of Naphthalene

Combustion Reactions

Combustion of propane:

C3H8 + O2

Combustion of methane:

CH4 + O2

Combustion of butene (this one is tricky!)

C4H6 + O2

Teacher Demo Extraordinaire!

What is a flame video- Science Friday

http://www.sciencefriday.com/video/06/08/2012/what-is-a-flame.html

Recap: 5 Types of Reactions

1. Combination

2. Decomposition

3. Single Replacement

4. Double Replacement

5. Combustion

Warm Up: Predict the products, balance and classify the following reactions.

Li + MgCl2

C6H12 + O2

Ca(NO3)2 + NaOH

Types of Rxns Lab

Take about 10 minutes to do the prelab questions on the lab. Most of the answers should be in your CB notes.

Warm Up-

Balance the following combustion equations:

C4H4 + O2 CO2 + H2O

C3H6 + O2 CO2 + H2O

C7H14 + O2 CO2 + H2O

Types of Reaction Lab

a. Synthesis: Mg + O2

b. Decomposition CuCO3

c. Single Replacement Zn + HCl

d. Double Replacement PbNO3 + KI

Finish the lab

You have 20 minutes to get it done!

Be sure that all your questions are answered!

Debrief Types of Rxns Lab

Types of Reaction Lab

Synthesis: Mg + O2

Did the mass of the system change after the reaction took place?

Did you detect the presence of ammonia gas?

Endothermic or exothermic?

Types of Reaction Lab

Decomposition CaCO3

What evidence indicates a chemical reaction.

How do you know that carbon dioxide was formed?

Endothermic or exothermic?

Types of Reaction Lab

Single Replacement

Zn + HCl

What evidence did you see?

What was in the little tube– how do you know?

Endothermic or exothermic?

Types of Reaction Lab

Double Replacement

PbNO3 + KI

What evidence did you see?

Endothermic or exothermic?

Work on classifying the types of reactions on your balancing WS.

When you finish, you can start working on the back side of the Current Mole WS…. The front side should be complete!

Warm Up

Balance and classify the following reactions:

1.Zn + H2SO4 → H2 + Zn(SO4)2

2.CaCl2 + NaNO3 → Ca(NO3)2 + NaCl

3.C3H8 + O2 → CO2 + H2O

You should have most of these WS done!

1.Balancing equations WS– classified rxn type

2. Mole Practice WS…

Finish both of these… turn them in!

Work on the Review!

Due the beginning of class on Monday!

Test after we go over the review!!

Warm Up

Balance and classify the following reactions:

1.Na + H2CO3 → H2 + Na2CO3

2. NaF + Ca(NO3)2 → NaNO3 + CaF2

3. C5H12 + O2 → CO2 + H2O

Warm Up- part 2

Determine the molar mass of MgF2

Convert 5.7 g of magnesium fluoride to moles.

Convert 6.3 g of magnesium fluoride to molecules.

Warm Up Quiz

1. Determine the molar mass of Na3PO4

2. How many moles in 10.6g of Na3PO4

3. How many atoms in 0.50 mol Al?

4. How many atoms in 3.6 g of carbon?

Warm Up

Balance and classify the following reactions:

1.K + H3PO4 → H2 + K3PO4

3. CH12 + O2 → CO2 + H2O