Chemical Reactions

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Chemical ReactionsChemical Equations
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Chemical Reactions
Chemical Change

• A process involving a substance or substances
  changing into a new substance or substances

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Chemical Reactions
Evidence of a chemical reaction
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Chemical Reactions
Evidence of a chemical reaction
1) A permanent color change
2) A gas is produced
3) Energy is exchanged
4) A precipitate is produced
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Chemical Equations

• A statement using chemical formulas to describe
  the identities and relative amounts of reactants
  and products involved in the chemical reaction

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• Reactant(s) ? Product(s)

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• MgCO3 ? MgO CO2

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• MgCO3 ? CO2 MgO

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• MgCO3 (s) ? MgO (s) CO2(g)

Phases of Components (s) solid (l)
liquid (g) gas (aq) aqueous
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Physical Change Vs. Chemical Change
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Physical Change
Chemical Change
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Physical Change
Chemical Change
Phase Changes Dissolving Mixing Breaking Separatin
g Filtering
Rearrange Atoms New Substances form
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Did a chemical change occur?

1. Permanent Color Change Occurs
2. Precipitate Formed
3. Gas is Released
4. Energy is Exchanged Temperature

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Chemical Reaction Demonstration

• Permanent Color Change
• CuSO4 (Aq) Zn (s) ? ZnSO4 (Aq) Cu (s)
• Blue Gray Clear Black
• The Zn and Cu are Switching, this is known as a
  single replacement Reaction.
• Gas is Produced
• HCl (l) Zn (s) ? ZnCl (Aq) H2 (g)
• Energy is Exchanged
• Mg (s) O2 (g) ? MgO (s)
• Rapid Oxidation
• Precipitate is Formed
• Pb(NO3)2 (Aq) K2CrO4 (Aq) ? KNO3 (Aq)
  PbCrO4 (s)
• Clear Bright Yellow

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Practice Exercise 1

• Define Chemical Reaction
• How do we know a chemical reaction has taken
  place?
• What is a Chemical Equation and Why do we use
  them?
• What are the initial constituents of a chemical
  reaction? What are the end products called?
• What do the following symbols stand for?
• s l g aq

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Types of Chemical Equations
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Synthesis

• Putting things together
• Also known as Direct Combination.

2 Na Cl2 2 NaCl 4 Al 3 O2 2 Al2O3
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Decomposition

• Breaking things down/Taking apart
• AKA Analysis

2 KClO3 2 KCl 3 O2 3 MnO2 Mn3O4 O2
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Single Replacement

• Replacing one element in a compound with another
  element.

2 Al 6 HCl 2 AlCl3 3 H2 2 NaBr Cl2
2 NaCl Br2
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Double Replacement

• Switching one element from a compound with
  another element from a different compound.

2 AgNO3 MgCl2 2 AgCl Mg(NO3)2 HCl
NaOH NaCl H2O
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Others

• Combustion
• Rapid Oxidation
• XXXX O2 CO2 H2O
• Oxidation
• Add Oxygen (Combustion)
• Reduction
• Acid Base Neutralization
• Etc

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HW

• Due Monday
• Read outline page 249-255

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Exothermic Reactions

• Release or give off heat.
• Heat is a byproduct of the reaction.
• Temperature increases as the bonds between
  products are formed.
• Examples
• Combustion, Respiration, Oxidation

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Endothermic Reactions

• Take in or absorb Heat from the surroundings.
• Temperature decreases as the reaction progresses.
• Heat is used to break bonds of reactants.
• Decomposition or Analysis Reactions

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Oxidation

• Removing Electrons

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Reduction

• Adding Electrons

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Rate of Reaction

• Reactions occur at different speeds.
• The time it takes for reactants to become
  products.

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Catalysts

• They speed up reactions without being affected
  themselves.
• They stay the same
• Enzymes in living organisms.
• Lowers activation energy
• The amount of energy needed to start a reaction.

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Speeding Up Reactions

• Temperature, Energy, Pressure, Surface Area,
  Concentration, Collisions, Catalyst.

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Measuring Rates of Reactions

• Measure Reactants
• Measure Products

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BalancingChemical Equations
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Reactant(s)
Product(s)
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• MgCO3 (s) ? MgO (s) CO2(g)

Phases of Components (s) (l) (g)
(aq)
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• 1 MgCO3 (s) ? 1 MgO (s) 1 CO2(g)

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• 1 MgCO3 (s) ? 1 MgO (s) 1 CO2(g)

Reactants
Products
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5 atoms
5 atoms

• 1 MgCO3 (s) ? 1 MgO (s) 1 CO2(g)

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• H2 O2 ? H2O

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• 2 H2 1 O2 ? 2 H2O

H2 H2 O2 ? H2O H2O
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• 2 H2 1 O2 ? 2 H2O

H2 H2 O2 ? H2O H2O
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• Ca Cl2 ? CaCl2

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• Na Cl2 ? NaCl

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• Fe2O3 ? Fe O2

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• AgNO3 NaCl ? NaNO3 AgCl

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• FeS2 O2 ? Fe2O3 SO2

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• 4 FeS2 11 O2 ? 2 Fe2O3 8 SO2

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• NH4OH Ni(NO3)2 ? NH4NO3 Ni(OH)2
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• NH4OH Ni(NO3)2 ? NH4NO3 Ni(OH)2
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• Na2CO3 Fe(NO3)3 ? Fe2(CO3)3 NaNO3

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Na2CO3 Fe(NO3)3 ? Fe2(CO3)3 NaNO3

• 3 Na2CO3 2 Fe(NO3)3 ? Fe2(CO3)3 6 NaNO3
• Balanced!!!

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• H3PO4 Ca(OH)2 ? Ca3(PO4)2 H2O

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•  NH4OH H3PO4 ? (NH4)3PO4 H2O
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• Al(OH)3 H2SO4 ? Al2(SO4)3 H2O
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• C6H6 O2 ? CO2 H2O