Chemical Change
part 2
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plus SET
The Periodic Table
Rules leading to correct formula
2. Positive ions usually form the first
part of the name (99% cases)
3. If the formula is correct there is no
overall charge
4. If you have more than one polyatomic
ion it is placed inside brackets
Please copy into your exercise books
1. Positive ions (cations) can join to
negative ions (anions)
+ 1 sodium Na
potassium K
hydrogen H
silver Ag
lithium Li
ammonium NH4
magnesium Mg
calcium Ca
barium Ba
zinc Zn
+2
copper Cu
+3
iron(11) Fe
aluminium Al
chromium Cr
iron(111) Fe
Negative ions
(Anions)
- 1 fluoride F
bromide Br
chloride Cl
hydroxide OH
nitrate NO3
nitrite NO2
hydrogencarbonate HCO3
-2
carbonate CO3
sulphide S oxide O
sulphate SO4
Essential training ions
Positive ions
(Cations)
sulphite SO3
chromate CrO4
- 3 nitride N
phosphate PO4
NaF
The easy way to
NaBr
learn these!
NaNO3
NaHCO3
NH4F
NH4Cl
NH4OH
(NH4)2CO3
(NH4)2S
N.B.
all numbers should
be lowercase and
subscript
Repeat this process linking each positive to
each
negative ion
Chemical Formulae
IONS
CHARGES
Ca
HCO3
FORMULA
calcium
hydrogencarbonate
NUMBERS
Chemical Formulae
IONS
CHARGES
Pb
PO4
FORMULA
lead(11) phosphate
NUMBERS
Chemical Formulae
IONS
CHARGES
NH4
Cr2O7
FORMULA
ammonium
dichromate
NUMBERS
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
In chemistry there are millions of chemical reactions.
But most reactions can be classified as
one of four types of reactions:
Synthesis (Composition)
In a synthesis reaction
(also known as a composition reaction),
two substances combine to form a larger substance.
C
+
O
O
O
C
O
Here are 3 synthesis reactions:
Hydrogen + oxygen yields water
2H2 + O2 -> 2H2O
Magnesium + nitrogen yields magnesium nitride
3Mg + N2 -> Mg3N2
Iron + sulphur yields iron(II) sulphide
Fe + S -> FeS
Write balanced chemical equations for the
following synthesis reactions
hydrogen + chlorine --------> hydrogen chloride
sodium + oxygen -----------> sodium oxide
nitrogen + hydrogen -------------->
H2 + Cl2 --------> 2HCl
4Na + 02 -------> 2Na2O
3H2 + N2 -------> 2NH3
ammonia
ANSWERS
UNDER
HERE
Mr G
Decomposition
In a decomposition reaction, a larger substance
breaks apart and forms two or more simpler substances.
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 -> 2H2O
With an electrical current, water can be
decomposed into hydrogen and oxygen gas.
2H2O -> 2H2 + O2
Some examples of decomposition
Heat copper carbonate and it will decompose
(Refer to flash animation .swf)
CuCO3 -> CuO + CO2
(Most carbonates decompose producing the oxide and carbon dioxide)
Heat lead(11) hydroxide and it will decompose
Pb(OH)2 -> PbO + H2O
Write balanced chemical equations to show
the following decompositions,
heat copper oxide + steam
copper hydroxide ------->
heat
sodium nitrate ---------> sodium nitrite + oxygen
heat
mercury(1) oxide ------> mercury + oxygen
heat
zinc nitrate ------> zinc oxide + nitrogen dioxide + oxygen
heat
calcium carbonate -------> calcium oxide + carbon dioxide
Solutions
QUESTION SOLUTIONS
UNDER HERE
Cu(OH)2 ------> CuO + H20
2NaNO3 ------> 2NaNO2 + 02
2Hg2O --------> 4Hg + O2
2Zn(N03)2 ------->2ZnO +4NO2 +
O2
CaCO3 --------> CaO + CO2
Single Replacement
In a single replacement reaction,
a more active element replaces
a less active element in a compound.
more reactive
less reactive
Single Replacement
Here Mg is more reactive than Pb
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 --> 2KF + Cl
No surprise! fluorine is more reactive than chlorine
Write balanced chemical equations for the
following single replacement reactions
magnesium + hydrochloric acid --->hydrogen + magnesium chloride
bromine + hydrogen iodide ---> hydrogen bromide + iodine
lithium + copper sulphate -----> lithium sulphate + copper
fluorine + sodium chloride ----> sodium fluoride + chlorine
zinc + nitric acid -----> zinc nitrate + hydrogen
Solutions here!
Mg + 2HCl ------> MgCl2 + H2
Br2 +2HI ------> 2HBr + I2
2Li + CuSO4 ------> Li2SO4 + Cu
F2 + 2NaCl -------> 2NaF + Cl2
Zn + 2HNO3 -----> Zn(NO3)2 + H2
A double replacement
change
Br
H
Na
O
+
Mg
O
Na
H
Br
What is reacting with what?
Look at arrows how do they
rearrange?
Double Replacements
H
O
Na
Br
Mg
+
Na
O
H
Br
Products from previous page
The whole chemical reaction
N
a
Br
Mg
O
O
O
H
+
H
Mg
+
H
Br
N
a
N
a
O
Br
H
+
Br
N
a
Mg(OH)2 + 2NaBr --> MgBr2 + 2NaOH
Notice the atoms or ions are just rearranged
The number of atoms on both sides of arrow are
the same
Now write equations for the following double
replacement reactions
? = unknown part
silver
+
nitrate
copper
sulphate
?
sodium
chloride
sodium
+
?
+
?
?
chloride
?
+
nitrate
copper
hydroxide
lead
iodide
+
+
?
nitrate
potassium
nitrate