Transcript Chemical Reactions - Saint Paul Public Schools

TYPES OF Reactions
Reactions can be categorized on the basis
of:
1. Heat changes- exothermic/ endothermic
2. Reactants and products- 5 types
3. Reduction and oxidation (REDOX)transfer of electrons.
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Types of Reactions
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There are five types of chemical
reactions we will talk about:
1.
2.
3.
4.
5.
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Synthesis reactions
_____________ reactions
Single displacement reactions
________________ reactions
Combustion reactions
You need to be able to identify the type
of reaction and predict the product(s)
Steps to Writing Reactions
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Some steps for doing reactions
1.
2.
3.
Identify the type of reaction
Predict the product(s) using the type of
reaction as a model
Balance it
Don’t forget about the diatomic elements!
(BrINClHOF) For example, Oxygen is O2 as an
element.
In a compound, it can’t be a diatomic element
because it’s not an element anymore, it’s a
compound!
1. Synthesis reactions
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Synthesis reactions occur when two
substances (generally elements) combine
and form a compound. (Sometimes these are
called combination or addition reactions.)
reactant + reactant  1 product
Basically: A + B  AB
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Example: 2H2 + O2  2H2O
Example: C + O2  CO2
Synthesis Reactions
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Here is another example of a synthesis
reaction
Practice
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Predict the products. Write and balance
the following synthesis reaction equations.
Sodium metal reacts with chlorine gas
Na(s) + Cl2(g) 
Solid Magnesium reacts with fluorine gas
Mg(s) + F2(g) 
Aluminum metal reacts with fluorine gas
Al(s) + F2(g) 
2. Decomposition Reactions
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Decomposition reactions occur when a
compound breaks up into the elements or
in a few to simpler compounds
1 Reactant  Product + Product
In general: AB  A + B
Example: 2 H2O  2H2 + O2
Example: 2 HgO  2Hg + O2
Decomposition Reactions
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Another view of a decomposition reaction:
Decomposition Exceptions
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Carbonates and chlorates are special case
decomposition reactions that do not go to
the elements.
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Carbonates (CO32-) decompose to carbon
dioxide and a metal oxide
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Chlorates (ClO3-) decompose to oxygen gas
and a metal chloride
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Example: CaCO3  CO2 + CaO
Example: 2 Al(ClO3)3  2 AlCl3 + 9 O2
There are other special cases, but we will not
explore those in Chemistry I
Practice
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Predict the products. Then, write and
balance the following decomposition
reaction equations:
Solid Lead (IV) oxide decomposes
PbO2(s) 
Aluminum nitride decomposes
AlN(s) 
Practice
Identify the type of reaction for each of the
following synthesis or decomposition
reactions, and write the balanced equation:
N2(g) + O2(g)  Nitrogen monoxide
BaCO3(s) 
Co(s)+ S(s)  (Co is +3)
NH3(g) + H2CO3(aq) (NH4)2CO3
NI3(s) N2 +I2
Practice p 292
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Aluminum oxide decomposes when
electricity passes through it.
Nickel (II) hydroxide decomposes to
produce nickel (II) oxide and water.
Heating sodium hydrogen carbonate
produces sodium carbonate and water.
Carbon dioxide gas is also produced.
3. Single Replacement Reactions
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Single Replacement Reactions occur when
one element replaces another in a compound.
A metal can replace a metal (+) OR
a nonmetal can replace a nonmetal (-).
element + compound product + product
A + BC  AC + B (if A is a metal) OR
A + BC  BA + C (if A is a nonmetal)
(remember the cation always goes first!)
When H2O splits into ions, it splits into
H+ and OH- (not H+ and O-2 !!)
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A more reactive metal will replace a less
reactive metal from a compound. The
Activity series of metals lists metals in
order of reactivity (p 293) and helps
decide whether or not the reaction will
occur.
Single Replacement Reactions
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Another view:
Activity series of metals
lithium, potassium, strontium, calcium
sodium , magnesium, aluminum
zinc, chromium ,iron, cadmium
cobalt, nickel, tin, lead
HYDROGEN
antimony, arsenic, bismuth, copper
 mercury
 Silver, paladium
platinum
gold
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Single Replacement Reactions
Write and balance the following single
replacement reaction equation:
• Zinc metal reacts with aqueous
hydrochloric acid
Zn(s) + 2 HCl(aq)  ZnCl2 + H2(g)
Note: Zinc replaces the hydrogen ion in the
reaction
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Single Replacement Reactions
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Sodium chloride solid reacts with fluorine gas
2 NaCl(s) + F2(g)  2 NaF(s) + Cl2(g)
Note that fluorine replaces chlorine in the compound
•
Aluminum metal reacts with aqueous copper
(II) nitrate
Al(s)+ Cu(NO3)2(aq)
Practice p 295
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Predict whether the following reactions
will occur. If a reaction occurs, write a
balanced equation for the reaction.
K(s)+ZnCl2(aq)-->
Cl2(g)+HF(aq)-->
Fe(s)+Na3PO4(aq)-->
Al(s)+Pb(NO3)2(aq)-->
4. Double Replacement Reactions
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Double Replacement Reactions occur
when a metal replaces a metal in a compound
and a nonmetal replaces a nonmetal in a
compound
Compound + compound  product +
product (insoluble product= precipitate)
AB + CD  AD + CB
Double Replacement Reactions
First and last ions go together + inside ions go
together
• Example:
AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq)
•
Another example:
K2SO4(aq) + Ba(NO3)2(aq)  2 KNO3(aq) + BaSO4(s)
Practice
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Predict the products. Balance the equation
5.
HCl(aq) + AgNO3(aq) 
CaCl2(aq) + Na3PO4(aq) 
Pb(NO3)2(aq) + BaCl2(aq) 
FeCl3(aq) + NaOH(aq) 
H2SO4(aq) + NaOH(aq) 
6.
KOH(aq) + CuSO4(aq) 
1.
2.
3.
4.
5. Combustion Reactions
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Combustion reactions
occur when a hydrocarbon
reacts with oxygen gas.
This is also called
burning!!! In order to burn
something you need the 3
things in the “fire
triangle”:
1) A Fuel (hydrocarbon)
2) Oxygen to burn it with
3) Something to ignite the
reaction (spark)
Combustion Reactions
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In general:
CxHy + O2  CO2 + H2O
Products in combustion are
ALWAYS carbon dioxide and
water. (although incomplete
burning does cause some byproducts like carbon monoxide)
Combustion is used to heat
homes and run automobiles
(octane, as in gasoline, is C8H18)
Combustion
Reactions
Edgar Allen Poe’s
drooping eyes and
mouth are potential
signs of CO
poisoning.
Combustion
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Example
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C5H12 + 8 O2  5 CO2 + 6 H2O
Write the products and balance the
following combustion reaction:
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C10H22 + O2 
Mixed Practice
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1.
2.
3.
4.
5.
State the type, predict the products, and
balance the following reactions:
BaCl2 + H2SO4 
C6H12 + O2 
Zn + CuSO4 
Cs + Br2 
FeCO3 
TYPES OF REACTIONS review
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NAME THE 5 TYPES OF REACTIONS AND
GIVE AN EXAMPLE OF EACH. (10 pts)
2. CATEGORIZE THE FOLLOWING BASED ON
REACTION TYPE:(5 pts)
A). 2H2 +O2 ---2H2 O
B). Cl2 +NaI--2NaCl +I2
C). CH4 +2O2 --CO2 +2H2O
D).Ca (OH)2 ---CaO + H2O
E). NaOH + KCl KOH + NaCl
1.
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3. WHICH CONDITION HAS TO BE FULFILLED
IN ORDER FOR A SINGLE DISPLACEMENT
REACTION TO OCCUR?(1 pt)
4. NAME THE TWO COMMON PRODUCTS OF
COMBUSTION REACTIONS.(1 pt)
5. Fill in the blanks with the correct products of this
reaction, and balance the equation:(2pts)
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PbCl2 + Na2SO4 -->
____ + _______
Acids + Bases
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Acids all contain H+ cations and an anion.
Bases all contain OH- anions and a cation,
except for weak bases such as NH3
When acids dissociate in water they
release H+ ions and their anions.
When bases dissociate in water they
release or form OH- ions and their cations.
Neutralization Reactions
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In the reaction of an acid with a base, the H+
from the acid combines with the OH- from the
base to make water
The cation from the base combines with the
anion from the acid to make the salt
acid + base salt + water
H2SO4(aq) + Ca(OH)2(aq)  CaSO4(aq) + 2 H2O(l)
The net ionic equation for a strong acid-strong
base reaction is always
H+ (aq) + OH- (aq)  H2O(l)
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Neutralization practice
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P 195 Q 39- Complete and balance the
following neutralization reactions.
Underline the salt A. HCl + KOH-->
RbOH + HNO3 -->
HClO4+NaOH-->
HBr+CsOH-->
Reactions of Metals with
Nonmetals (Oxidation-Reduction)
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The metal loses electrons and becomes a
cation (oxidation)
The nonmetal gains electrons and
becomes an anion (reduction)
In the reaction, electrons are transferred
from the metal to the nonmetal
Oxidation-Reduction Reactions
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Oxidation-reduction reactions:
reactions that involve a transfer of one or
more electrons
The substance that loses electrons in the
reaction is oxidized. The substance that
gains electrons in the reaction is
reduced.
Another Kind of
Oxidation-Reduction Reaction
Some reactions between two non-metals
are also oxidation-reduction reaction.
 Any reaction in which O2 is a reactant or a
product will be an oxidation-reduction
reaction.
CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g)
2 SO3(g)  2 SO2(g) + O2(g)
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Self check p 183
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For each reaction, show how electrons are gained
and lost.
A. 2Na(s)+ Br2(l)--> 2NaBr(s)
B. 2Ca(s)+ O2(g)--> 2CaO(s)
P 196 Q 49- Balance each redox reaction. In
each, indicate which substance is being oxidized
and which is being reducedA. Na + S--> Na2S
B. Mg +O2-->MgO
C. Ca +F2--> CaF2
Fe +Cl2-->FeCl3
Total Ionic Equations
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Once you write the molecular equation
(synthesis, decomposition, etc.), you should
check for reactants and products that are
soluble or insoluble.
We usually assume the reaction is in water
We can use a solubility table to tell us which
compounds dissolve in water.
If the compound is soluble (does dissolve in
water), then split the compound into its
component ions
If the compound is insoluble (does NOT dissolve
in water), then it remains as a compound
Solubility Table
Solubilities Not on the Table!
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Gases only slightly dissolve in water
Strong acids and bases dissolve in water
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Hydrochloric, Hydrobromic, Hydroiodic, Nitric,
Sulfuric, Perchloric Acids
Group I hydroxides (should be on your chart anyway)
Water slightly dissolves in water! (H+ and OH-)
SrSO4 is insoluble; BeI2 and the products are
soluble
 There are other tables and rules that cover more
compounds than your table!
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Self check p 175
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Predict whether a solid will form when the
following parts of solutions are mixed. If
so, identify the solid and write the
balanced equation for the reactionBa(NO3)2(aq) and NaCl(aq)
Na2S(aq) and Cu(NO3)2(aq)
NH4Cl(aq) and Pb(NO3)2(aq)
Total Ionic Equations
Molecular Equation:
K2CrO4 + Pb(NO3)2 
PbCrO4 + 2 KNO3
Soluble
Insoluble
Soluble
Soluble
Total Ionic Equation:
2 K+ + CrO4 -2 + Pb+2 + 2 NO3- 
PbCrO4 (s) + 2 K+ + 2 NO3-
Net Ionic Equations
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These are the same as total ionic equations, but
you should cancel out ions that appear on BOTH
sides of the equation (termed as spectator ions)
Total Ionic Equation(complete):
2 K+ + CrO4 -2 + Pb+2 + 2 NO3- 
PbCrO4 (s) + 2 K+ + 2 NO3Net Ionic Equation:
CrO4 -2 + Pb+2  PbCrO4 (s)
Net Ionic Equations
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Try this one! Write the molecular, total ionic, and net
ionic equations for this reaction: Silver nitrate reacts
with Lead (II) Chloride in hot water.
Molecular:
Total Ionic:
Net Ionic:
Self check p 177
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For each of the following reactions, write the
molecular equation, the complete ionic equation,
and the net ionic equation.
Aqueous sodium sulfide is mixed with aqueous
copper (II) nitrate to produce solid copper (II)
sulfide and aqueous sodium nitrate.
Aqueous ammonium chloride and aqueous lead
(II) nitrate react to form lead (II) chloride and
aqueous ammonium nitrate.
Study guide for balancing
equations- Chapter 6
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Basic structure of equations- reactants,
products, arrow, physical state.
Signs of a chemical change.
Law of conservation of matter.
Rules for balancing equations.
Balancing equations.
Study guide for Types of
reactions and net ionic
equations- Chapter 7
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types of reactions- definitions,
examples, identification – synthesis,
decomposition, single and double
displacement, combustion,
neutralization and redox!
net ionic equations- solubility,
cancelling ions, spectator ions