Chemical Change

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Chemical Change part 2
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The Periodic Table
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Rules leading to correct formula
1. Positive ions (cations) can join to negative
ions (anions)
2. Positive ions usually form the first part of
the name (99 cases)
3. If the formula is correct there is no overall
charge
Please copy into your exercise books
4. If you have more than one polyatomic ion it is
placed inside brackets
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Positive ions (Cations)
Negative ions (Anions)
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- 1
fluoride F
sodium Na
chloride Cl
potassium K
bromide Br
hydroxide OH
hydrogen H
nitrate NO3 nitrite NO2
Essential training ions
lithium Li
silver Ag
hydrogencarbonate HCO3
ammonium NH4
- 2
carbonate CO3
magnesium Mg
2
oxide O
calcium Ca
sulphide S
barium Ba
zinc Zn
sulphate SO4
iron(11) Fe
sulphite SO3
copper Cu
chromate CrO4
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- 3
nitride N
aluminium Al
chromium Cr
phosphate PO4
iron(111) Fe
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NaF NaBr NaNO3 NaHCO3
The easy way to learn these!
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NH4F NH4Cl NH4OH (NH4)2CO3 (NH4)2S
N.B. all numbers should be lowercase and subscript
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Repeat this process linking each positive to
each negative ion
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calcium hydrogencarbonate
Chemical Formulae
CHARGES
IONS
NUMBERS
Ca
HCO3
FORMULA
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Chemical Formulae
lead(11) phosphate
CHARGES
IONS
NUMBERS
Pb
PO4
FORMULA
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ammonium dichromate
Chemical Formulae
CHARGES
IONS
NUMBERS
NH4
Cr2O7
FORMULA
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Try these 1. lithium sulphite 2. barium
hydroxide 3. copper carbonate 4. hydrogen
sulphide 5. magnesium nitride 6. ammonium
bromide 7. aluminium oxide.
Li2SO3 Ba(OH)2 CuCO3 H2S Mg3N2 NH4Br Al2O3
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In chemistry there are millions of chemical
reactions. But most reactions can be classified
as one of four types of reactions
Synthesis A B -gt AB Decomposition AB -gt A
B Single Replacement A BC -gt AC B Double
Replacement AB CD -gt AD CB
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Synthesis (Composition)
In a synthesis reaction (also known as a
composition reaction), two substances combine to
form a larger substance.

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Here are 3 synthesis reactions Hydrogen
oxygen yields water
2H2 O2 -gt 2H2O
Magnesium nitrogen yields magnesium nitride
3Mg N2 -gt Mg3N2
Iron sulphur yields iron(II) sulphide
Fe S -gt FeS
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Write balanced chemical equations for the
following synthesis reactions
hydrogen chlorine --------gt hydrogen chloride
sodium oxygen -----------gt sodium oxide
nitrogen hydrogen --------------gt ammonia
ANSWERS UNDER HERE Mr G
H2 Cl2 --------gt 2HCl
4Na 02 -------gt 2Na2O
3H2 N2 -------gt 2NH3
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Decomposition
In a decomposition reaction, a larger substance
breaks apart and forms two or more simpler
substances.
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The first thing you may notice about a
decomposition reaction is that it is the
complete opposite of a synthesis reaction. In
fact many synthesis reactions can be reversed
into a decomposition reaction.
When you burn hydrogen gas, the hydrogen
combines with oxygen to produce water.
2H2 O2 -gt 2H2O
With an electrical current, water can be
decomposed into hydrogen and oxygen gas.
2H2O -gt 2H2 O2
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Some examples of decomposition
Heat copper carbonate and it will
decompose (Refer to flash animation .swf) CuCO3
-gt CuO CO2
(Most carbonates decompose producing the oxide
and carbon dioxide)
Heat lead(11) hydroxide and it will decompose
Pb(OH)2 -gt PbO H2O
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Write balanced chemical equations to show the
following decompositions,
heat
copper hydroxide -------gt copper oxide steam
heat
sodium nitrate ---------gt sodium nitrite oxygen
heat
mercury(1) oxide ------gt mercury oxygen
heat
zinc nitrate ------gt zinc oxide nitrogen
dioxide oxygen
heat
calcium carbonate -------gt calcium oxide carbon
dioxide
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QUESTION SOLUTIONS UNDER HERE
Solutions Cu(OH)2 ------gt CuO H20 2NaNO3
------gt 2NaNO2 02 2Hg2O --------gt 4Hg
O2 2Zn(N03)2 -------gt2ZnO 4NO2 O2 CaCO3
--------gt CaO CO2
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Single Replacement
In a single replacement reaction, a more active
element replaces a less active element in a
compound.
more reactive
less reactive
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Single Replacement
Here Mg is more reactive than Pb
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Single Replacement
If fluorine gas is bubbled through a solution of
potassium chloride, the fluorine will replace
the chlorine.
This reaction can be represented as follows
2KCl F --gt 2KF Cl
No surprise! fluorine is more reactive than
chlorine
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Write balanced chemical equations for the
following single replacement reactions
magnesium hydrochloric acid ---gthydrogen
magnesium chloride
bromine hydrogen iodide ---gt hydrogen bromide
iodine
lithium copper sulphate -----gt lithium sulphate
copper
fluorine sodium chloride ----gt sodium fluoride
chlorine
zinc nitric acid -----gt zinc nitrate hydrogen
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Solutions here!
Mg 2HCl ------gt MgCl2 H2 Br2 2HI ------gt
2HBr I2 2Li CuSO4 ------gt Li2SO4 Cu F2
2NaCl -------gt 2NaF Cl2 Zn 2HNO3 -----gt
Zn(NO3)2 H2
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A double replacement change

What is reacting with what?
Look at arrows how do they rearrange?
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Double Replacements

Products from previous page
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The whole chemical reaction



Mg(OH)2 2NaBr --gt MgBr2 2NaOH
Notice the atoms or ions are just rearranged The
number of atoms on both sides of arrow are the
same
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Now write equations for the following double
replacement reactions
? unknown part
? chloride
silver nitrate
? nitrate
sodium chloride


? nitrate
copper hydroxide
sodium ?
copper sulphate


?
lead iodide
potassium nitrate
?