Transcript Unit Five: Chemical Reactions

Unit Five: Chemical Reactions
•I D E N T I F Y A N D B A L A N C E 5 T Y P E S O F
REACTIONS
•E X P E R I M E N T A L L Y D E T E R M I N E I N D I C A T O R S
OF A REACTION
Chemical Reactions
 Process by which the
atoms of one or more
substances are
rearranged to form
different substances
 Law of Conservation
of Matter – Matter is
not created or
destroyed during a
chemical reaction.
Evidence of a Chemical Reaction
Formation of a gas

Bubbles

Smell
2. Formation of a solid (precipitate) from two aqueous
solutions; often solids are colorful

“Snow globe” effect

“Paint” look

“Jello” consistency
3. Change in temperature

Test tube feels colder to you (endothermic reaction)

Test tube feels warmer to you (exothermic reaction)
1.
Writing Chemical Equations
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Read a description of the reaction
Note what is reacted with what
Note what is yielded or produced
Write formulas for each compound
Use + to represent “and”
Use  to represent “produces” or “yields”
Include states of matter where available
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(s) solid
(l) liquid
(g)gas
(aq) dissolved in water
Balancing Chemical Equations
 Write the skeleton equation.
 BE SURE THE FORMULAS ARE WRITTEN
CORRECTLY.
 Inventory reactants
 Inventory products
 Insert coefficients to make atoms of each
element equal on both sides of the equation
 Reduce the coefficients if possible
Writing & Balancing Equations Handout
1.
2.
Zn + Pb(NO3)2 --> Zn(NO3)2 + Pb
AlBr3 + Cl2 --> AlCl3 + Br2
Writing & Balancing Equations
1.
2.
3.
Zn + Pb(NO3)2 --> Zn(NO3)2 + Pb
2 AlBr3 + 3 Cl2 --> 2 AlCl3 + 3 Br2
Na3PO4 + CaCl2 --> Ca3(PO4)2 + NaCl
Writing & Balancing Equations
1.
2.
3.
Zn + Pb(NO3)2 --> Zn(NO3)2 + Pb
2 AlBr3 + 3 Cl2 --> 2 AlCl3 + 3 Br2
2 Na3PO4 + 3 CaCl2 --> Ca3(PO4)2 + 6 NaCl
Complete 4, 5, 6, and 8 on your own.
Potassium metal and chlorine gas
combine to form potassium chloride.
Select the balanced chemical equation.
A.) K+1 + Cl- --> KCl
B.) K + Cl --> KCl
C.) K + Cl2 --> KCl
D.) 2K + Cl2 --> 2KCl
Aluminum and hydrochloric acid react
to form aluminum chloride and
hydrogen gas.
Select the balanced chemical equation.
A.) Al+3 + HClO3 --> AlCl + H
B.) Al + 2HClO3 --> AlCl3 + H2
C.) Al + HCl --> AlCl3 + H2
D.) 2Al + 2HCl --> 2AlCl3 + 3H2
E.) 2Al + 6HCl --> 2AlCl3 + 3H2
Calcium hydroxide and phosphoric acid
react to form calcium phosphate and
water.
Select the balanced chemical equation.
A.) CaOH2 + H3P --> Ca3(PO4)2 + H2O
B.) 3CaOH2 + 2H3PO4 --> Ca3(PO4)2 + 6H2O
C.) 3Ca(OH)2 + H32PO4 --> Ca3(PO4)2 + 3H2O
D.) 3Ca(OH)2 + 2H3PO4 --> Ca3(PO4)2 + 6H2O
Hydrogen gas and nitrogen monoxide
react to form water and nitrogen gas.
Select the balanced chemical equation.
A.) 2H + NO --> H2O + N
B.) 6H + N2O3 --> 3H2O + 2N
C.) 2H2 + 2NO --> 2H2O + N2
D.) H2 + 2NO --> H2O + N2
Difficult Equations to Balance
Copper and sulfuric acid react to form copper
(II) sulfate and water and sulfur dioxide.
Cu + 2 H2SO4 --> CuSO4 + 2 H2O + SO2
Writing & Balancing Equations
1.
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8.
Zn + Pb(NO3)2 --> Zn(NO3)2 + Pb
2 AlBr3 + 3 Cl2 --> 2 AlCl3 + 3 Br2
2 Na3PO4 + 3 CaCl2 --> Ca3(PO4)2 + 6 NaCl
2 K + Cl2 --> 2 KCl
2 Al + 6 HCl --> 2 AlCl3 + 3 H2
3 Ca(OH)2 + 2 H3PO4 --> Ca3(PO4)2 + 6 H2O
Cu + 2 H2SO4 --> CuSO4 + 2 H2O + SO2
2 H2 + 2 NO --> 2 H2O + N2
5 Types of Chemical Reactions
 Synthesis
 Combustion
 Decomposition
 Double-Replacement
 Single-Replacement
Five Types of Reactions Clip
Synthesis Reactions
 A + B --> AB
 2 or more compounds or elements go together
to build a more complex compound
Synthesis Reaction Clip
Write the balanced chemical equation for the
reaction shown in the video clip.
2Al + 3Br2  2AlBr3
Combustion Reactions
 Oxygen combines with a substance and
releases energy in the form of heat and light
 DIATOMIC OXYGEN IS ALWAYS A
REACTANT!
Combustion Reaction Clip
In the video, the combustion reaction occurring in
the flask used up all of the oxygen gas in flask. A
vacuum formed as a result, and the egg was drawn
into the flask.
Decomposition Reactions
 A single compound breaks down into 2 or
more elements or new compounds
 AB --> A + B
Decomposition Reaction Clip
In the video, hydrogen peroxide is decomposed to form
hydrogen gas and oxygen gas. Many bubbles indicated
this gas production. A catalyst of KI was used to speed up
the decomposition reaction.
Double Replacement Reactions
 Exchange of ions between 2 ionic compounds
 AX + BY  AY + BX
 Often produce a precipitate
 Solid, liquid, or gas product formed from two “aqueous”
solutions
 Aqueous means dissolved in water.
 Example: Cobalt (II) chloride reacts with sodium
phosphate to produce cobalt (II) phosphate and
sodium chloride.
Single Replacement Reactions
 One element replaces another element in a
compound
 A + BX --> AX + B
 A metal will not always replace another metal.
The reactivity of the metal is important to
consider.
Only a more active metal replaces a less active metal.
 A less active metal will not replace a more active metal.
The reaction will simply not occur.

 Use the metal activity series to determine if
single replacement reactions occur.
Colored Pencil Corrections
9-2 Practice Problems (odd)
NH3 + HCl  NH4Cl
3. BaO + H2O  Ba(OH)2
5. Zn + Cu(NO3)2  Zn(NO3)2 + Cu
7. Fe + H2SO4  FeSO4 + H2
9. Co + Cl2  CoCl2
11. N2O5 + H2O  2HNO3
13. C + 2ZnO  2Zn + CO2
15. PCl3 + Cl2  PCl5
17. CaH2 + 2H2O  Ca(OH)2 + 2H2
19. C3H8 + 5O2  3CO2 + 4H20
1.
As you come in,
 The Materials:
Remote control
 Periodic table
 Pick up an “Intro to Chemical Reactions Investigations” handout
 The Plan:
 I-Respond Warm-Up – Types of Reactions Practice Quiz
 Instructions for “Intro to Chemical Reactions Investigations”
 Collaborative investigations in the lab
 The Assessments:
 TOMORROW – Types of Chemical Equations Quiz
 Thursday – Writing and Balancing Equations Quiz
 Friday – Predicting Products and Balancing Equations Quiz
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1. When grilling burgers with your friends on
Saturday evening, your propane tank and gas grill
work together to perform the following reaction:
C3H8 + O2  CO2 + H2O
A.) Synthesis
B.) Decomposition
C.) Combustion
D.) Single Replacement
E.) Double Replacement
2. If not stored properly, your hydrogen peroxide
can cause a mess in your medicine cabinet.
Hydrogen peroxide quickly breaks down in the
presence of light to produce oxygen gas and
hydrogen gas.
A.) Synthesis
B.) Decomposition
C.) Combustion
D.) Single Replacement
E.) Double Replacement
3. The white precipitate formed by acid rain on a
marble statue is produced in the following reaction:
CaCO3(aq)+H2SO4(aq)CaSO4(s)+H2CO3(aq)
A.) Synthesis
B.) Decomposition
C.) Combustion
D.) Single Replacement
E.) Double Replacement
9-2 Practice Problems (even)
2. CaCO3  CaO + CO2
4. CH3CHO  CH4 + CO
6. CaSO3  CaO + SO2
8. C2H6N2  C2H6 + N2
10. MnI2  Mn + I2
12. 2Mg + TiCl4  2MgCl2 + Ti
14. Br2 + 2NaI  2NaBr + I2
16. 2P + 3Br2  2PBr3
18. H2SO4 + 2KOH  K2SO4 + 2H2O
20. 2C6H6 + 15O2  12CO2 + 6H2O
Predicting Products & States of Matter
52. 2Al + 6HCl  2AlCl3 + 3H2
Predicting Products & States of Matter
52. 2Al(s) + 6HCl(aq)  2AlCl3(aq) + 3H2(g)
56.ZnCl2 + (NH4)2S  2NH4Cl + ZnS
Predicting Products & States of Matter
56.ZnCl2 (aq)+ (NH4)2S(aq)  2NH4Cl(aq) + ZnS(s)
59. HgSO4 + 2NH4NO3  Hg(NO3)2 + (NH4)2SO4
Predicting Products & States of Matter
59. HgSO4(aq) + 2NH4NO3(aq)  Hg(NO3)2(aq) +
(NH4)2SO4(aq)
60. Fe + CuSO4  FeSO4 + Cu
Predicting Products & States of Matter
60. Fe (s)+ CuSO4 (aq)  FeSO4 (aq) + Cu (s)
67. Br2 + 2NaI  2NaBr + I2
Predicting Products & States of Matter
67. Br2 (l) + 2NaI(aq)  2NaBr (aq) + I2 (g)
Colored Pencil Corrections
 Al(NO3)3 + NaOH = Al(OH)3 + NaNO3
 KClO3 = KCl + O2
 H3PO4 + Mg(OH)2 = Mg3(PO4)2 + H2O
 NH4NO2 = N2 + H2O
 BaCl2 + Na2SO4 = NaCl + BaSO4
 Fe2O3 + CO = Fe + CO2
 Mg(OH)2 + (NH4)3PO4 = Mg3(PO4)2 + NH3 + H2O
Reactions in Aqueous Solution
 More than 70% of earth is covered by water
 66% of the human body is water
 MANY chemical reactions occur in water
 Often form solids called precipitates
 Remember: Ionic compounds dissociate in water.
Net Ionic Equations
 Represent reactions of ionic compounds in
aqueous solution by writing complete ionic
equations
 Remove spectator ions (those appear on both sides
of the equation but aren’t in the precipitate)
 Leaves a net ionic equation that can be balanced
Chemical Reactions Pre-Lab
 Why do I set up the lab with so many aqueous
solutions?
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Rate of Reaction
 Temperature – warmer = faster reaction; particles
are moving faster
 Concentration - # of particles; more particles =
faster reaction
 State of Matter – dissolved means greater surface
area; more surface area = faster reaction
 Surface Area - Filings, shot, powder, mossy, etc.;
greater surface area = faster reaction
 Catalyst – DOES NOT REACT; lowers the activation
energy of the reaction