Transcript ch8 - Otterville R-VI School District

 What
is the difference between a
chemical and physical reaction?
 When you watch a reaction occur,
what are some hints that it is a
chemical reaction?
Ch. 8 Chemical Equations
and Reactions
8.1 Describing Chemical
Reactions
Chemical Reactions
 when
a substance
changes identity


reactants- original
products- resulting
 law
of conservation
of mass

total mass of reactants =
total mass of products
Chemical Reactions
 chemical


equation
represents identities and relative
amounts of reactants and products in the
chemical reaction
uses symbols and formulas
Hints of Chemical Rxn
 heat

can also happen with
physical changes
 gas

or light
bubbles
means a gas is being
created as product
 precipitate

solid is being created
 color
change
Writing Chemical Equations

most pure elements


diatomic molecules




written as elemental symbol
molecule containing only 2
atoms
some elements normally exist
this way
H2, O2, N2, F2, Cl2, Br2, I2, At2
other exceptions


sulfur: S8
phosphorus: P4
Word Equations
 uses
names instead of formulas
 helps you to write formula equation
Example
 Description:
Solid sodium oxide is added to water
at room temperature and forms
sodium hydroxide.
 Word Equation:
sodium oxide + water  sodium hydroxide
 Formula
Equation:
Na2O + H2O  NaOH
Symbols Used in Equations
yields
reversible
above arrow:
or heat
MnO2 or Pt
25°C
2 atm
heated
catalyst
specific T
requirement
specific P
requirement
after a formula:
(s) solid
(l)
liquid
(aq) aqueous:
dissolved in
water
(g)
gas
Coefficients
 whole
numbers in front of formula
 distributes to numbers of atoms in
formula
 specifies the relative number of moles
and molecules involved in the reaction
 used to balance the equation
Equations cannot tell us:
 if

the reaction will actually occur
depends on many factors affecting energy
 the


speed of the reaction
depends on chemical kinetics
can be very slow, almost unnoticeably
 how

the bonding actually changes
formula may not clearly show bonding
 Write
the word equation from the
following description:
Zinc metal is added to hydrochloric
acid to create zinc chloride and
hydrogen gas.
Ch. 8 Chemical Equations
and Reactions
8.1b Balancing Equations and
Writing Formula Equations
Balancing Equations

1.
2.
3.
4.
5.
6.
ONLY add/change coefficientsNEVER subscripts!!!
balance one type of atom at a time
balance polyatomic ions first
balance atoms that appear only once
second
balance H and O last
simplify if you can
Check at end!
Writing Equations




Write Word equations to help you
organize reactants and products
Be sure to include symbols showing
states of each reactant and product
Be sure to write the correct formula
for each (crossing over for ionic
compounds!)
Check your balancing of the equation
when you are finished
Example 1
 Description:
Zinc metal is added to hydrochloric
acid to create zinc chloride and
hydrogen gas.
 Word Equation:
zinc + hydrochloric acid 
zinc chloride + hydrogen
Example 1
 Formula
Equation:
Zn (s) + HCl(aq)  ZnCl2(aq) + H2(g)
 Balanced
Formula Equation
Zn (s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
Example 2
 Solid
calcium metal reacts with water
to form aqueous calcium hydroxide
and hydrogen gas.
 calcium + water 
calcium hydroxide + hydrogen
 Ca(s) + H2O(l)  Ca(OH)2(aq) + H2(g)
 Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g)
Example 3
 solid
zinc metal reacts with aqueous
copper (II) sulfate to produce solid
copper metal and aqueous zinc sulfate
 zinc
+ copper (II) sulfate 
copper + zinc sulfate
 Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)
 Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)
Example 4
 Hydrogen
peroxide in an
aqueous solution
decomposes to produce
oxygen and water
 hydrogen peroxide 
oxygen + water
 H2O2(aq)  O2(g) + H2O(l)
 2H2O2(aq)  O2(g) + 2H2O(l)
Example 5
 Solid
copper metal reacts with
aqueous silver nitrate to produce solid
silver metal and aqueous copper (II)
nitrate
 copper + silver nitrate 
silver + copper (II) nitrate

Cu(s) + AgNO3(aq)  Ag(s) + Cu(NO3)2(aq)

Cu(s) + 2AgNO3(aq)  2Ag(s) + Cu(NO3)2(aq)
Example 6

Carbon dioxide gas is bubbled through
water containing solid barium carbonate,
creating aqueous barium bicarbonate
carbon dioxide + water + barium carbonate
 barium bicarbonate
 CO2(g) + H2O(l) + BaCO3(s)  Ba(HCO3)2(aq)
 CO2(g) + H2O(l) + BaCO3(s)  Ba(HCO3)2(aq)

Example 7
Acetic acid solution is added to a solution
of magnesium bicarbonate to create water,
carbon dioxide gas, and aqueous
magnesium acetate.
 acetic acid + magnesium bicarbonate 
water + carbon dioxide + magnesium acetate
 HCH3COO(aq) + Mg(HCO3)2(aq) 
H2O(l) + CO2(g) + Mg(CH3COO)2(aq)
 2HCH3COO(aq) + Mg(HCO3)2(aq) 
2H2O(l) + 2CO2(g) + Mg(CH3COO)2(aq)

 Write
the balanced formula equation
for:
Lithium metal is added to a solution
of aluminum sulfate to make aqueous
lithium sulfate and aluminum metal.
Ch. 8 Chemical Equations
and Reactions
8.2a Types of Chemical
Reactions
Types of Chemical Reactions
5
basic types discussed here
 not all reactions fall in these
categories
 you should be able to:


categorize a reaction by its reactant(s)
predict the product(s)
1. Synthesis
 also
called composition reaction
 reactants:


more than one
can be elements or compounds
 products:
only one compound
A + X  AX
where A is the cation and X is anion
1. Synthesis
 Rubidium
and sulfur
Rb(s) + S8(s)  Rb2S(s)
 Magnesium and oxygen
Mg(s) + O2(g)  MgO(s)
 Sodium and chlorine
Na(s) + Cl2(g)  NaCl(s)
 Magnesium and fluorine
Mg(s) + F2(g)  MgF2(s)
1. Synthesis
 calcium
oxide and water
CaO(s) + H2O(l)  Ca(OH)2(aq)
 sulfur
dioxide and water
SO2(g) + H2O(l)  H2SO3(aq)
 calcium
oxide and sulfur dioxide
CaO(s) + SO2(g)  CaSO3(s)
2. Decomposition
 opposite
of synthesis
 usually require energy
 reactants: only one compound
 products: more than one

usually elements but can be compounds
AX  A + X
2. Decomposition
 water
H2O(l)  H2(g) + O2(g)
 calcium carbonate
CaCO3(s)  CaO(s) + CO2(g)
 calcium hydroxide
Ca(OH)2(s)  CaO(s) + H2O(l)
 carbonic acid
H2CO3(aq)  CO2(g) + H2O(l)
3. Single Replacement
 an
element replaces a similar element
in a compound
 reactants: 1 element & 1 compound
 products: 1 element & 1 compound
A + BX  B + AX
Y + AX  X + AY
3. Single Replacement
 zinc
and hydrochloric acid
Zn(s) + HCl(aq)  ZnCl2(aq) + H2(g)
 iron and water
Fe(s) + H2O(l)  FeO(aq)
 magnesium and lead (II) nitrate
Mg(s) + Pb(NO3)2(aq)  Mg(NO3)3(aq) + Pb(s)
 chlorine and potassium bromide
Cl2(g) + KBr(s)  KCl(s) + Br2(g)
4. Double Replacement
 two
similar elements switch places
 reactants: 2 compounds
 products: 2 compounds
AX + BY  BX + AY
4. Double Replacement
 barium
chloride and sodium sulfate
BaCl2(aq) + Na2SO4(aq)  NaCl(aq) + BaSO4(s)
 iron sulfide and hydrochloric acid
FeS(aq) + HCl(aq)  FeCl2(aq) + H2S(g)
 hydrochloric acid and sodium hydroxide
HCl(aq) + NaOH  NaCl(aq) + H2O(l)
 potassium iodide and lead (II) nitrate
KI(aq) + Pb(NO3)2  KNO3(aq) + PbI2(s)
5. Combustion
 combines
with oxygen
 releases energy in form of heat/light
 reactants: O2 + compound/element

compound or element must be made of C
and H only
 H2O

and/or CO2
depending on element contained in
reactants
Ex: CH4 + O2  CO2 + H2O
Combustion
 hydrogen
and oxygen
H2(g) + O2(g)  H2O(g)
 propane
and oxygen
C3H8(g) + O2(g)  CO2(g) + H2O(g)
Practice
Classify each of the following reactions
one of the five basic types:
 Na2O + H2O  NaOH
 Zn (s) + 2HCl(aq)  ZnCl2(aq) + H2(g)
 Ca(s) + 2H2O(l)  Ca(OH)2(aq) + H2(g)
Practice
 2H2O2(aq)
 Cu(s)
 O2(g) + 2H2O(l)
+ 2AgNO3(aq)  2Ag(s) +Cu(NO3)2(aq)
 C2H4(g)
 ZnO(s)
+ O2(g)  CO2(g) + H2O(g)
+ C(s)  2Zn(s) + CO2(g)
Practice
 Na2O(s)
 Ca(s)
+ 2CO2(g) + H2O(l)  NaHCO3(s)
+ H2O(l)  Ca(OH)2 (aq) + H2(g)
 KClO3(s)
 KCl(s) + O2(g)
 H2SO4(aq)
+ BaCl2(aq)  HCl(aq) + BaSO4(s)
 Write
the balanced formula equation
for the following reaction
 Identify the type of reaction
 Aqueous lead (II) nitrate was mixed
with a hydrochloric acid to create lead
(II) chloride and nitric acid.
Ch. 8 Chemical Equations
and Reactions
8.2b Predicting Products of
Chemical Reactions
Types of Reactions
 we
are going to learn how to predict
products in simple reactions of each
type
 will need to identify type for more
complex reactions but not predict
products
1. Synthesis
 making
binary compounds
 find ions created by each reactant
 crossover to make product
 barium metal is reacted with solid
sulfur.

Ba(s) + S8(s)  BaS(s)
 magnesium

metal reacts with bromine
Mg(s) + Br2(l)  MgBr2(s)
2. Decomposition
 of
binary compounds
 find elements that will be created
 write them in natural state
 Solid silver oxide is heated.

Ag2O(s)  Ag(s) + O2(s)
 Water

undergoes decomposition.
H2O(l)  H2(g) + O2(g)
3. Single Replacement
 Identify
the “similar” element in the
compound that it will replace
 Find ions created
 crossover to make new compound
 zinc metal is added to solution of
lead(II) nitrate

Zn(s) + Pb(NO3)2(aq)  Zn(NO3)2(aq) + Pb(s)
 sodium

iodide is added to chlorine gas
NaI(aq) + Cl2(g)  NaCl(aq) + I2(s)
4. Double Replacement
 identify
which parts will switch places
 find ions that will be created
 crossover to create new compounds
 silver nitrate and sodium chloride
solutions are mixed

AgNO3(aq) + NaCl(aq)  NaNO3(aq) + AgCl(s)
 solutions
of magnesium fluoride and
potassium hydroxide are mixed

MgF2(aq) + KOH(aq)  Mg(OH)2(aq) + KF(aq)
5. Combustion
 always
makes H2O and/or CO2
 choose based on what elements exist
in reactants
 solid

carbon reacts with oxygen
C(s) + O2(g)  CO2 (g)
 C2H5OH

reacts with oxygen in air.
C2H5OH + O2(g)  CO2(g) + H2O(l)
Example
 Identify
the type of reaction, predict
the products, and write the balanced
chemical equation:
 Hydrogen sulfide gas is bubbled
through a solution of potassium
hydroxide
Example
 Liquid
butanol (C4H9OH) is burned in
oxygen gas.
 compound + oxygen: C
 C4H9OH (l) + 6O2(g)
 5H2O(l) + 4CO2(l)
 Liquid bromine is mixed with sodium
iodide solution.
 element + compound: SR
 Br2(l) + 2NaI(aq)  2NaBr + I2
Example
 Calcium
metal is heated strongly in
nitrogen gas.
 2 elements: S
 N2(g) + 3Ca(s)  Ca3N2
 Liquid water is decomposed through
electrolysis.
 1 compound: D
 2H2O(l)  2H2(g) + O2(g)
Ch. 8 Chemical Equations
and Reactions
8.3 Activity Series
Activity Series
 Activity

ability of an element to react
 easier
it reacts, higher the activity
 activity


series
list of elements organized according to
activities
from highest to lowest
Activity Series
 metals


greater activity, easier to lose electrons
easier to become a cation
 nonmetals


greater activity, easier to gain electrons
easier to become an anion
Activity Series
 used
to predict whether single
replacement reactions will occur
 most
 an
active is on top
element can replace anything below
it but not any above it
Practice
 zinc
and hydrofluoric acid
 calcium
 copper
and lead (II) nitrate
and lithium sulfate
 bromine
and iron (II) chloride