Start Up41309

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Start Up 4/13/09

• List 3 pieces of evidence that a chemical
  reaction has occurred.
• Give 2 examples of a chemical reaction. (Think
  back to the beginning of the year when we
  discussed chemical change.)

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Chemical Reactions

• 5 Types of Chemical Reactions and Balancing
  Equations

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Core Content Terms (Ch. 10)

• Chemical equation
• Catalyst
• Coefficient
• Balanced Equation
• Synthesis Rxn.

• Decomposition Rxn.
• Single-replacement Rxn.
• Double-replacement Rxn.
• Combustion Rxn.
• Net Ionic Equation

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Bookwork for Chapter 11

• Chapter 11
• Problems 10-12, 22, 24, 45, 51

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Parts of a Chemical Equation

• X Y XY

• Need to Know
• (s)
• (g)
• (l)
• (aq)
• cat.
• heat

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Recall Diatomic Molecules...

• Remember the seven N, O, F, Cl, Br, I, H
• Must be written as

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Recall

• Ionic and Covalent Compounds will be back again!
  
• And remember those oxidation numbers

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Chemical Reaction Activity

• Each group (of 2) will get an envelope.
• You must arrange your elements to make a chemical
  equation.
• Record the equation on a sheet of paper. (1
  paper per group)
• Each group must have 10 complete equations on
  their paper.
• Dont worry about numbers of atoms today. Just
  types of atoms.
• You should be prepared to share your responses.

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Start Up 4/14/09

• Write a chemical equation for the following
  scenarios
• Calcium reacts with Bromine to form ________.
• C3H8 reacts with Oxygen to form Carbon Dioxide
  and Water.

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5 Types of Chemical Reactions

• 1. Synthesis
• A B AB
• two things combine to form one
• magnesium reacts with oxygen, when heated, to
  form magnesium oxide

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• 2. Decomposition
• AB A B
• one compound breaks down into two or more
  elements/compounds
• hydrogen peroxide decomposes to form water
  vapor and oxygen

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• 3. Single Replacement
• A BC B AC
• element compound --gt
• new element new compound
• aluminum reacts with copper (II) chloride to
  form copper and aluminum chloride

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• 4. Double Replacement
• AB CD AD CB
• compound compound --gt
• new compound new compound
• silver nitrate and sodium chloride react to
  form silver chloride and sodium nitrate

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• 5. Combustion
• hydrocarbon O2 CO2 H2O
• methane reacts with oxygen, when heated, to
  form carbon dioxide and water vapor

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BalancingWhy?
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Conservation of Mass

• Matter cannot be created or destroyed
• In a chemical reaction, all the atoms present at
  the beginning are still present at the end
• Total mass cannot change
• Total mass of the reactants total mass of the
  products

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Combustion of Methane

• Methane gas burns to produce carbon dioxide gas
  and liquid water
• whenever something burns it combines with O2(g)
• CH4(g) O2(g) ? CO2(g) H2O(l)

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Combustion of Methane Balanced

• To show the reaction obeys the Law of
  Conservation of Mass it must be balanced
• CH4(g) 2 O2(g) ? CO2(g) 2 H2O(l)

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Balancing Chemical Equations

• Balanced chemical equation contains same number
  of each kind of atom on each side of the arrow
• 2 H2 (g) O2 (g) ? 2 H2O (l)
• 2 x 2 H 4 H 2 x 2 H 4 H
• 1 x 2 O 2 O 2 x 1 O 2 O

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Steps to follow

• Write the unbalanced equation.
• Inventory the atoms in the reactants and in the
  products.
• Balance the equation.
• Tips
• Balance elements left-to-right on the Periodic
  Table (metals first, then nonmetals)
• Leave H and O until last
• Balance Polyatomic Ions as groups
• Example Write H2O as H-OH

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1. Write the unbalanced equation.
__Zn (s) __HCl (aq) ? __ZnCl2 (aq) __ H2 (g)
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2. Inventory (Talley) reactants and products.
__Zn (s) __HCl (aq) ? __ZnCl2 (aq) __ H2 (g)
Zn Cl H
Zn Cl H
1 1 1
1 2 2
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3.Balance by changing coefficients only--NEVER
change SUBSRIPTS
2
__Zn (s) __HCl (aq) ? __ZnCl2 (aq) __ H2 (g)
Zn Cl H
Zn Cl H
1 1 1
1 2 2
2 2
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Balance this reaction
__CH4 (g) __O2 (g) ? __CO2 (g) __H2O (l)
2
2
C H O
1 2 3
C H O
1 4 2
4
4
4
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Try to balance this reaction
2
__KClO3 (s) ? __KCl (s) __O2 (g)
2
3
K Cl O
1 1 2
2
2
K Cl O
1 1 3
2
2
6
6
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Try to balance this reaction
2
3
6
__Al(OH)3(s) __H2SO4(aq) ? __Al2(SO4)3(aq)
__H2O(l)
Al S H O
2 3 2 13
2
Al S H O
1 1 5 7
3
12
8
12
18
10
18
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What do the numbers mean?In terms of molecules
C3H8 (g) 5 O2 (g) ? 3 CO2 (g) 4 H2O (l)
1 molecule C3H8 3 C atoms 8 H atoms 44.0 amu
5 molecules O2 10 O atoms 5 (32.0 amu) 160.0
amu
3 molecules CO2 3 C atoms 6 O atoms 3 (44.0
amu) 132.0 amu
4 molecules H2O 8 H atoms 4 O atoms 4 (18.0
amu) 72.0 amu
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Balance these equations

• __ Mg __ O2 ? __ MgO
• __ KClO3 ? __ KCl __ O2
• __ Cu __ AgNO3? __ Cu(NO3)2 __ Ag
• __KOH __ H3PO4 ? __ K3PO4 __ H2O
•  

• 2 Mg O2 ? 2 MgO
• 2 KClO3 ? 2 KCl 3 O2
• Cu 2 AgNO3? Cu(NO3)2 2 Ag
• 3 KOH H3PO4 ? K3PO4 3 H2O

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? Chemistry Song ?

• Due Monday, November 19
• Ideas
• I will bring one from last year tomorrow.
• http//organicsongs.cos.ucf.edu/

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Start Up 4/15/09

• Identify the type of reaction and balance each
• S8 O3 ---gt SO2
• NaCl H2SO4 ---gt Na2SO4 HCl

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Start Up 4/16/09

• Predict the product(s) and balance
• ___KI ___Pb(NO3)2 ?

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Caution! Goggles Required!

• You are using acids and bases and fire today.
• Hot water bath is not on a hot plate, it is over
  a Bunsen burner. Use caution!
• Wash all glassware with DI water to prevent
  contamination.
• Copper Nitrate can be a skin irritant.
• Pipets contain your reagents.
• Do not throw them away.
• Do not put anything else in them.
• Do not squirt anyone with them!

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Copper Cycle Lab

• Everyone must turn in own lab data sheet
• Each group must have
• Title
• Purpose
• Hypothesis
• includes predictions of observations for each
  reaction and overall lab
• Materials
• Conclusion which must include
• Summary of results
• Comparison to hypothesis
• Error analysis
• Suggestions for improvements or changes for
  future study

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2 people per group

• Materials Partner
• Responsible for
• Obtaining materials
• Refilling reagents
• Cleaning lab station
• Recorder
• Responsible for
• Observations
• All written lab sections

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Start Up 4/21/09

• Use the following to create a balanced chemical
  equation
• CaCl2 , CaCO3 , NaCl , Na2CO3

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Debrief Copper Lab
Al wire
HNO3
HCl
NaOH
Heat
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What factors influence the rate of a chemical
reaction?
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Rates of Reaction depend on

• Temperature
• Concentration of reactant
• Catalyst
• Surface area of solid reactant
• Pressure of gaseous reactants or products

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Notebook Check! 4/22/09

• During the video, you need to show me the 2 start
  ups I ask for. Each person may be differentHave
  all start ups from this unit ready.
• No copying last minute! Both lender and copier
  will get zeroes!

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SourcesThanks!

• www.hse.k12.in.us/staff/kbowen/Assignments/Steps2
  0to20balancing20Chemical20equations.pdf
• http//www.usoe.org/curr/science/sciber00/8th/matt
  er/sciber/chemtype.htm