BALANCING EQUATIONS

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BALANCING EQUATIONS CHEMICAL REACTIONS
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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

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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!

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Balancing Equations

• In every balanced equation
• each side of the equation
• has the same number of atoms
• of each element

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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
• Heat
• Pressure
• Temperature
• Catalyst
• Reversible reaction

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Balance this equation

• NaNO3 CrCl3 ? NaCl Cr(NO3)3
• How would you write it?

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Combination Reactionor Synthesis Reaction

• Two or more simple substances react to form a
  more complicated one
• A B ? AB
• Fe S ? FeS

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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 reactions
• How would we say these equations?

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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

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Decomposition Reactions

• Harder to predict the productsalways remember
  your diatomics.
• Water is often a product!
• HgO(s) ?
• NH4NO3?

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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!!

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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

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Single Replacement Reactions

• Easy to predict the products. Look at the ions
  remember that a cation has to bond to an anion!!
• Dont forget about diatomics!
• Zn(s) H2SO4(aq) ?
• Na(s) H2O ?
• OOPS! Did we balance them?

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Single Replacement Reactions

• Zn(s) H2SO4(aq) ?
• Zn(s) H2SO4(aq) ? ZnSO4(aq) H2(g)
• Na(s) H2O ?
• Na(s) HOH-(l) ?
• 2Na(s) 2HOH-(l) ? 2NaOH H2(g)

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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.

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Metal Reactivity

Increases down a group Decreases across a
period
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• Brainiacs-- Metal Reactivity

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Reactivity in Single Displacement

• Cs KMnO4 ? CsMnO4
• Will this occur??
• Na KMnO4 ? NaMnO4 K
• Will this occur?

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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

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Double Replacement Reactions

• Generally take place between two ionic compounds
  in aqueous solution
• Pb(NO3)2 2KI ? PbI2 2KNO3

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Double Replacement Reactions

• 2NaCl H2SO4 ?

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Double Replacement Reactions

• Ca(OH)2(aq) 2HCl(aq) ?)

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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

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Combustion Reactions

• Combustion of propane
• C3H8 O2 ?
• Combustion of methane
• CH4 O2 ?
• Combustion of butene (this one is tricky!)
• C4H6 O2 ?

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Teacher Demo Extraordinaire!
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• What is a flame video- Science Friday
• http//www.sciencefriday.com/video/06/08/2012/what
  -is-a-flame.html

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Recap 5 Types of Reactions

• Combination
• Decomposition
• Single Replacement
• Double Replacement
• Combustion

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

• Li MgCl2 ?
• C6H12 O2 ?
• Ca(NO3)2 NaOH ?

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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.

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Warm Up-

• Balance the following combustion equations
• C4H4 O2 ? CO2 H2O
• C3H6 O2 ? CO2 H2O
• C7H14 O2 ? CO2 H2O

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Types of Reaction Lab

• a. Synthesis Mg O2
• b. Decomposition CuCO3
• c. Single Replacement Zn HCl
• d. Double Replacement PbNO3 KI

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Finish the lab

• You have 20 minutes to get it done!
• Be sure that all your questions are answered!

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Debrief Types of Rxns Lab
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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?

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Types of Reaction Lab

• Decomposition CaCO3 ?
• What evidence indicates a chemical reaction.
• How do you know that carbon dioxide was formed?
• Endothermic or exothermic?

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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?

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Types of Reaction Lab

• Double Replacement
• PbNO3 KI ?
• What evidence did you see?
• Endothermic or exothermic?

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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!

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Warm Up

• Balance and classify the following reactions
• Zn H2SO4 ? H2 Zn(SO4)2
• CaCl2 NaNO3 ? Ca(NO3)2 NaCl
• C3H8 O2 ? CO2 H2O

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You should have most of these WS done!

• 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!!

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Warm Up

• Balance and classify the following reactions
• Na H2CO3 ? H2 Na2CO3
• 2. NaF Ca(NO3)2 ? NaNO3
  CaF2
• 3. C5H12 O2 ? CO2 H2O

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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.

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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?

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Warm Up

• Balance and classify the following reactions
• K H3PO4 ? H2 K3PO4
• 3. CH12 O2 ? CO2 H2O