additional science

1. 04/25/16
Chemistry 2Chemistry 2
W Richards
The Weald School

2. 04/25/16
The structure of the atomThe structure of the atom
ELECTRON –
negative, mass
nearly nothing
PROTON –
positive, same
mass as
neutron (“1”)
NEUTRON –
neutral, same
mass as proton
(“1”)
The Ancient Greeks used to believe that
everything was made up of very small particles.
I did some experiments in 1808 that proved
this and called these particles ATOMS:
Dalton

3. 04/25/16
Mass and atomic numberMass and atomic number
Particle Relative Mass Relative Charge
Proton 1 +1
Neutron 1 0
Electron Very small -1
MASS NUMBER = number of
protons + number of neutrons
SYMBOL
PROTON NUMBER = number of
protons (obviously)

4. 04/25/16
Mass and atomic numberMass and atomic number
How many protons, neutrons and electrons?

5. 04/25/16
IsotopesIsotopes
An isotope is an atom with a different number of neutrons:
Each isotope has 8 protons – if it didn’t then it just
wouldn’t be oxygen any more.
Notice that the mass number is different. How many
neutrons does each isotope have?

6. 04/25/16
Electron structureElectron structure
Consider an atom of Potassium:
Potassium has 19 electrons.
These electrons occupy
specific energy levels “shells”…
Nucleus
The inner shell has __ electrons
The next shell has __ electrons
The next shell has __ electrons
The next shell has the remaining __ electron
Electron structure
= 2,8,8,1

7. 04/25/16
Periodic Table IntroductionPeriodic Table Introduction

8. 04/25/16
Mendeleev
Periodic tablePeriodic table
The periodic table arranges all the elements
in groups according to their properties.
Horizontal rows are called PERIODS
Vertical
columns are
called GROUPS

9. 04/25/16
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg
The Periodic TableThe Periodic Table
Fact 1: Elements in the same group have the
same number of electrons in the outer shell
(this corresponds to their group number)
E.g. all group 1 metals
have __ electron in
their outer shell
These elements
have __ electrons
in their outer shell
These elements have
__ electrons in their
outer shells

10. 04/25/16
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg
The Periodic TableThe Periodic Table
Fact 2: As you move down through the periods
an extra electron shell is added:
E.g. Lithium has 3
electron in the
configuration 2,1
Potassium has 19 electrons in
the configuration __,__,__,__
Sodium has 11
electrons in the
configuration 2,8,1

11. 04/25/16
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg
The Periodic TableThe Periodic Table
Fact 3: Most of the elements are metals:
These elements
are metals
This line divides
metals from non-
metals
These elements
are non-metals

12. 04/25/16
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Fe Ni Cu Zn Br Kr
Ag I Xe
Pt Au Hg
The Periodic TableThe Periodic Table
Fact 4: (Most important) All of the elements
in the same group have similar PROPERTIES.
This is how I thought of the periodic table in
the first place. This is called PERIODICITY.
E.g. consider the group 1 metals. They all:
1) Are soft
2) Can be easily cut with a knife
3) React with water

13. 04/25/16
CompoundsCompounds
Compounds are formed
when two or more
elements are
chemically combined.
Some examples:
Glucose
Methane
Sodium
chloride (salt)

14. 04/25/16
Some simple compounds…Some simple compounds…
Methane, CH4 Water, H2O
Carbon
dioxide, CO2
Ethyne, C2H2
Sulphuric
acid, H2SO4
Key
Hydrogen
Oxygen
Carbon
Sulphur

15. 04/25/16
Balancing equationsBalancing equations
Consider the following reaction:
Na O
H H
H H
Na
O
H
Sodium + water sodium hydroxide + hydrogen
+ +
This equation doesn’t balance – there are 2 hydrogen
atoms on the left hand side (the “reactants” and 3 on
the right hand side (the “products”)

16. 04/25/16
Balancing equationsBalancing equations
We need to balance the equation:
Na
O
H H
H H
Na
O
H
Sodium + water sodium hydroxide + hydrogen
+ +
Na
O
H H
Na
O
H
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

17. 04/25/16
Some examplesSome examples
Mg + O2
Zn + HCl
Fe + Cl2
NaOH + HCl
CH4 + O2
Ca + H2O
NaOH + H2SO4
CH3OH + O2
MgO
ZnCl2 + H2
FeCl3
NaCl + H2O
CO2 + H2O
Ca(OH)2 + H2
Na2SO4 + H2O
CO2 + H2O
2
2
2 3
2
2
2
2 3
2
2
2
2
2 4

18. 04/25/16
BondingBonding
Hi. My name’s Johnny Chlorine.
I’m in Group 7, so I have 7
electrons in my outer shell
I’d quite like to have a full outer
shell. To do this I need to GAIN
an electron. Who can help me?
Cl
Cl

19. 04/25/16
BondingBonding
Here comes one of my friends,
Harry Hydrogen
Hey Johnny. I’ve only got one
electron but it’s really close to
my nucleus so I don’t want to lose
it. Fancy sharing?
Cl
H
Cl H
Now we’re both really stable.
We’ve formed a covalent bond.

20. 04/25/16
BondingBonding
Here comes another friend,
Sophie Sodium
Hey Johnny. I’m in Group 1 so I have
one electron in my outer shell. Unlike
Harry, this electron is far away from
the nucleus so I’m quite happy to get
rid of it. Do you want it?
Cl
Now we’ve both got full outer shells
and we’ve both gained a charge.
We’ve formed an IONIC bond.
Na
Okay
Cl Na
+-

21. 04/25/16
Covalent bondingCovalent bonding
Consider an atom of hydrogen:
Notice that hydrogen has just __ electron in its outer
shell. A full (inner) shell would have __ electrons, so two
hydrogen atoms get together and “_____” their electrons:
Now they both have a ____ outer shell and are
more _____. The formula for this molecule is H2.
When two or more atoms bond by sharing electrons we
call it ____________ BONDING. This type of bonding
normally occurs between _______ atoms. It causes the
atoms in a molecule to be held together very strongly
but there are ____ forces between individual molecules.
This is why covalently-bonded molecules have low melting
and boiling points (i.e. they are usually ____ or ______).
Words – gas, covalent, non-metal, 1, 2, liquid, share, full, weak, stable

22. 04/25/16
Dot and Cross DiagramsDot and Cross Diagrams
H
OH
Water, H2O:

23. 04/25/16
Dot and Cross DiagramsDot and Cross Diagrams
Oxygen, O2:
O O

24. 04/25/16
Dot and cross diagramsDot and cross diagrams
Water, H2O:
Oxygen, O2:
OH H
O O
H
H
O
O O
Step 1: Draw the atoms with
their outer shell:
Step 2: Put the atoms together and
check they all have a full outer shell:

25. 04/25/16
Dot and cross diagramsDot and cross diagrams
Nitrogen, N2:
Carbon dioxide, CO2:Ammonia NH3:
Methane CH4:
H HN
H
HH
H
H
C
N N
O OC

26. 04/25/16
Other ways of drawing covalent bondsOther ways of drawing covalent bonds
Consider ammonia (NH3):
H HN
H
H HN
H
H HN
H

27. 04/25/16
IonsIons
An ion is formed when an atom gains or loses electrons and
becomes charged:
If we “take away” the electron
we’re left with just a positive
charge:
This is called an ion (in this case, a positive hydrogen ion)
+
-
+
The electron is negatively charged
The proton is positively charged
+

28. 04/25/16
Ionic bondingIonic bonding
Na
Na
+
This is where a metal bonds with a non-metal (usually). Instead of sharing
the electrons one of the atoms “_____” one or more electrons to the
other. For example, consider sodium and chlorine:
Sodium has 1 electron on its outer shell
and chlorine has 7, so if sodium gives
its electron to chlorine they both have
a ___ outer shell and are ______.
A _______
charged
sodium ion
A _________
charged
chloride ion
As opposed to covalent bonds, ionic bonds form strong forces
of attraction between different ions due to their opposite
______, causing GIANT IONIC STRUCTURES to form (e.g
sodium chloride) with ______ melting and boiling points:
Cl
Cl
-

29. 04/25/16
Some examplesSome examples
Mg
Magnesium
chloride:
MgCl2
Cl
Cl
+
Mg
2+ Cl
-
Cl
-
Calcium oxide:
CaO
OCa + Ca
2+
O
2-

30. 04/25/16
Giant structures (“lattices”)Giant structures (“lattices”)
+
+
+
+
+++
+
+
1. Diamond – a giant
covalent structure with a
very ____ melting point
due to ______ bonds
between carbon atoms
2. Graphite – carbon atoms
arranged in a layered
structure, with free _______
in between each layer enabling
carbon to conduct _________
3. Sodium chloride – a giant ionic lattice
with _____ melting and boiling points
due to ______ forces of attraction.
Can conduct electricity when _______.
4. Metals – the
__________ in metals
are free to move around
(“delocalised”), holding
the _____ together
and enabling it to
conduct _________

31. 04/25/16
A closer look at metalsA closer look at metals
+
+
+
+
+++
+
+
Metals are defined as elements that readily
lose electrons to form positive ions. There
are a number of ways of drawing them:
+
-
+
-
+
-
+- + -
+
-
+
-
+
-
+ + +
+ + +
+ +
Delocalised electrons

32. 04/25/16
NanoscienceNanoscience
Nanoscience is a new branch of science that refers to
structures built from a few hundred atoms and are 1-
100nm big. They show different properties to the same
materials in bulk. They also have a large surface area to
volume ratio and their properties could lead to new
developments in computers, building materials etc.
Definition:
Task: research nanoscience and find two current and/or
future applications of this science.

33. 04/25/16
Group 1 – The alkali metalsGroup 1 – The alkali metals
Li
Na
K
Rb
Cs
Fr

34. 04/25/16
Group 1 – The alkali metalsGroup 1 – The alkali metals
1) These metals all have ___
electron in their outer shell.
Some facts…
2) Reactivity increases as you go _______ the group. This is because the
electrons are further away from the _______ every time a _____ is
added, so they are given up more easily.
3) They all react with water to form an alkali (hence their name) and
__________, e.g:
Words – down, one, shell, hydrogen, nucleus, decreases
Potassium + water potassium hydroxide + hydrogen
2K(s) + 2H2O(l) 2KOH(aq) + H2(g)
2) Density increases as you go down the
group, while melting point ________

35. 04/25/16
Group 0 – The Noble gasesGroup 0 – The Noble gases
He
Ne
Ar
Kr
Xe
Rn

36. 04/25/16
Group 0 – The Noble gasesGroup 0 – The Noble gases
Some facts…
1) All of the noble gases have a full
outer shell, so they are very ______
2) They all have _____ melting and
boiling points
3) They exist as single atoms rather then _________ molecules
4) Helium is ________ then air and is used in balloons and
airships (as well as for talking in a silly voice)
5) Argon is used in light bulbs
(because it is so unreactive) and
argon , krypton and ____ are used
in fancy lights
Words – neon, stable, low, diatomic, lighter

37. 04/25/16
Group 7 – The halogensGroup 7 – The halogens
F
Cl
Br
I
At

38. 04/25/16
Group 7 – The HalogensGroup 7 – The Halogens
Some facts…
1) Reactivity DECREASES
as you go down the group
Decreasing
reactivity
(This is because the electrons are further away from the
nucleus and so any extra electrons aren’t attracted as much).
2) They exist as
diatomic molecules (so
that they both have a
full outer shell):
Cl Cl
3) Because of this fluorine and chlorine are liquid at room
temperature and bromine is a gas

39. 04/25/16
The halogens – some reactionsThe halogens – some reactions
1) Halogen + metal:
Na
+
Cl
-
Na Cl+
2) Halogen + non-metal:
H Cl+ Cl H
Halogen + metal ionic salt
Halogen + non-metal covalent molecule

40. 04/25/16
Atomic massAtomic mass
SYMBOL
PROTON NUMBER = number of
protons (obviously)
RELATIVE ATOMIC MASS, Ar
(“Mass number”) = number of
protons + number of neutrons

41. 04/25/16
Relative formula mass, MRelative formula mass, Mrr
The relative formula mass of a compound is the relative atomic
masses of all the elements in the compound added together.
E.g. water H2O:
Therefore Mr for water = 16 + (2x1) = 18
Work out Mr for the following compounds:
1) HCl
2) NaOH
3) MgCl2
4) H2SO4
H=1, Cl=35 so Mr = 36
Na=23, O=16, H=1 so Mr = 40
Mg=24, Cl=35 so Mr = 24+(2x35) = 94
H=1, S=32, O=16 so Mr = (2x1)+32+(4x16) = 98
Relative atomic mass of O = 16
Relative atomic mass of H = 1

42. 04/25/16
A “Mole”A “Mole”
Definition:
A mole of a substance is the relative formula
mass of that substance in grams
For example, 12g of carbon would be 1 mole of carbon...
...and 44g of carbon dioxide (CO2) would be 1 mole etc...

43. 04/25/16
Calculating percentage massCalculating percentage mass
If you can work out Mr then this bit is easy…
Calculate the percentage mass of magnesium in magnesium oxide, MgO:
Ar for magnesium = 24 Ar for oxygen = 16
Mr for magnesium oxide = 24 + 16 = 40
Therefore percentage mass = 24/40 x 100% = 60%
Percentage mass (%) =
Mass of element Ar
Relative formula mass Mr
x100%
Calculate the percentage mass of the following:
1) Hydrogen in hydrochloric acid, HCl
2) Potassium in potassium chloride, KCl
3) Calcium in calcium chloride, CaCl2
4) Oxygen in water, H2O

44. 04/25/16
Recap questionsRecap questions
Work out the relative formula mass of:
1) Carbon dioxide CO2
2) Calcium oxide CaO
3) Methane CH4
Work out the percentage mass of:
1) Carbon in carbon dioxide CO2
2) Calcium in calcium oxide CaO
3) Hydrogen in methane CH4

45. 04/25/16
Calculating the mass of a productCalculating the mass of a product
E.g. what mass of magnesium oxide is produced when 60g of
magnesium is burned in air?
Step 1: READ the equation:
2Mg + O2 2MgO
IGNORE the
oxygen in step 2 –
the question
doesn’t ask for it
Step 3: LEARN and APPLY the following 3 points:
1) 48g of Mg makes 80g of MgO
2) 1g of Mg makes 80/48 = 1.66g of MgO
3) 60g of Mg makes 1.66 x 60 = 100g of MgO
Step 2: WORK OUT the relative formula masses (Mr):
2Mg = 2 x 24 = 48 2MgO = 2 x (24+16) = 80

46. 04/25/16
Work out Mr: 2H2O = 2 x ((2x1)+16) = 36 2H2 = 2x2 = 4
1. 36g of water produces 4g of hydrogen
2. So 1g of water produces 4/36 = 0.11g of hydrogen
3. 6g of water will produce (4/36) x 6 = 0.66g of hydrogen
Mr: 2Ca = 2x40 = 80 2CaO = 2 x (40+16) = 112
80g produces 112g so 10g produces (112/80) x 10 = 14g of CaO
Mr: 2Al2O3 = 2x((2x27)+(3x16)) = 204 4Al = 4x27 = 108
204g produces 108g so 100g produces (108/204) x 100 = 52.9g of Al O
1) When water is electrolysed it breaks down into hydrogen and oxygen:
2H2O 2H2 + O2
What mass of hydrogen is produced by the electrolysis of 6g of water?
3) What mass of aluminium is produced from 100g of aluminium oxide?
2Al2O3 4Al + 3O2
2) What mass of calcium oxide is produced when 10g of calcium burns?
2Ca + O2 2CaO

47. 04/25/16
Another methodAnother method
Try using this equation:
Mass of product IN GRAMMES
Mass of reactant IN GRAMMES
Mr of product
Mr of reactant
Q. When water is electrolysed it breaks down into hydrogen and oxygen:
2H2O 2H2 + O2
What mass of hydrogen is produced by the electrolysis of 6g of water?
Mass of product IN GRAMMES
6g
4
36
So mass of product = (4/36) x 6g = 0.66g of hydrogen

48. 04/25/16
Problems with this techniqueProblems with this technique
Calculating the amount of a product may not always give you a
reliable answer...
1) The reaction may not have completely _______
2) The reaction may have been _______
3) Some of the product may have been ____
4) Some of the reactants may have produced other _______
The amount of product that is made is called the “____”.
This number can be compared to the maximum theoretical
amount as a percentage, called the “percentage yield”.
Words – lost, yield, finished, reversible, products

49. 04/25/16
Atom EconomyAtom Economy
Percentage
atom economy =
Relative formula mass of useful product
Total masses of products
Calculate the atom economies of the following:
1) Converting ethanol into ethene (ethene is the useful bit):
C2H5OH C2H4 + H20
2) Making zinc chloride from zinc and hydrochloric acid:
Zn + 2HCl ZnCl2 + H2

50. 04/25/16
Numbers of molesNumbers of moles
Consider two liquids:
Now consider two gases:
20cm3
of 0.1mol/dm3
of
hydrochloric acid
20cm3
of 0.1mol/dm3
of
sodium hydroxide
These two beakers contain the same number of moles
20cm3 of helium at room
temperature and pressure
20cm3 of argon at room
temperature and pressure
These two gases contain the same number of moles

51. 04/25/16
Endothermic and exothermic reactionsEndothermic and exothermic reactions
Step 1: Energy must
be SUPPLIED to
break bonds:
Step 2: Energy is
RELEASED when new
bonds are made:
A reaction is EXOTHERMIC if more energy is RELEASED
then SUPPLIED. If more energy is SUPPLIED then is
RELEASED then the reaction is ENDOTHERMIC
Energy
Energy

52. 04/25/16
Example reactionsExample reactions
Reaction Temp. after mixing/O
C Exothermic or
endothermic?
Sodium hydroxide + dilute
hydrochloric acid
Sodium
hydrogencarbonate +
citric acid
Copper sulphate +
magnesium powder
Sulphuric acid +
magnesium ribbon

53. 04/25/16
Reversible ReactionsReversible Reactions
Some chemical reactions are reversible. In other words, they
can go in either direction:
A + B C + D
NH4Cl NH3 + HCl
e.g. Ammonium chloride Ammonia + hydrogen chloride
If a reaction is EXOTHERMIC in one direction
what must it be in the opposite direction?
For example, consider copper sulphate:
Hydrated copper
sulphate (blue)
Anhydrous copper
sulphate (white)
+ Heat + Water
CuSO4 + H2OCuSO4.5H2O

54. 04/25/16
Reversible ReactionsReversible Reactions
When a reversible reaction occurs in a CLOSED SYSTEM (i.e. no reactants
are added or taken away) an EQUILIBRIUM is achieved – in other words,
the reaction goes at the same rate in both directions:
A + B C + D
Endothermic reactions
Increased temperature:
Decreased temperature:
A + B C + D
A + B C + D
More products
Less products
Exothermic reactions
Increased temperature:
Decreased temperature:
A + B C + D
Less products
More products
A + B C + D

55. 04/25/16
Making AmmoniaMaking Ammonia
Nitrogen + hydrogen Ammonia
N2 + 3H2 2NH3
•High pressure
•450O
C
•Iron catalyst
Recycled H2 and N2
Nitrogen
Hydrogen
Mixture of NH3, H2 and
N2. This is cooled
causing NH3 to liquefy.
Fritz Haber,
1868-1934
Guten Tag. My name is Fritz Haber and I won the Nobel
Prize for chemistry. I am going to tell you how to use a
reversible reaction to produce ammonia, a very
important chemical. This is called the Haber Process.
To produce ammonia from nitrogen and hydrogen
you have to use three conditions:

56. 04/25/16
Haber Process: The economicsHaber Process: The economics
A while ago we looked at reversible reactions:
A + B C + D
Endothermic, increased temperature
A + B C + D
Exothermic, increase temperature
ExothermicEndothermic
1) If temperature was DECREASED the amount of ammonia formed would
__________...
2) However, if temperature was INCREASED the rate of reaction in both
directions would ________ causing the ammonia to form faster
3) If pressure was INCREASED the amount of ammonia formed would
INCREASE because there are less molecules on the right hand side of
the equation
Nitrogen + hydrogen Ammonia
N2 + 3H2 2NH3

57. 04/25/16
Haber Process SummaryHaber Process Summary
•200 atm pressure
•450O
C
•Iron catalyst
Recycled H2 and N2
Nitrogen
Hydrogen
Mixture of NH3, H2
and N2. This is
cooled causing NH3
to liquefy.
To compromise all of these factors, these conditions are used:
A low temperature increases the yield of ammonia but is too
slow
A high temperature improves the rate of reaction but
decreases the yield too much
A high pressure increases the yield of ammonia but costs a lot
of money

58. 04/25/16
Rates of ReactionRates of Reaction
Hi. I’m Mike Marble. I’m
about to have some acid
poured onto me. Let’s see
what happens…
Here comes an acid
particle…
It missed!
Here comes another
one. Look at how
slow it’s going…
No effect! It didn’t
have enough energy!
Oh no! Here comes
another one and it’s
got more energy…

59. 04/25/16
Rates of ReactionRates of Reaction
View animation
Chemical reactions occur when different
atoms or molecules _____ with enough
energy (the “________ Energy):
Basically, the more collisions we get the _______ the
reaction goes. The rate at which the reaction happens
depends on four things:
1) The _______ of the reactants,
2) Their concentration
3) Their surface area
4) Whether or not a _______ is used
Words – activation, quicker, catalyst, temperature, collide

60. 04/25/16
CatalystsCatalysts
Task
Research and find out about two uses of catalysts in industry,
including:
1) Why they are used
2) The disadvantages of each catalyst

61. 04/25/16
Catalyst SummaryCatalyst Summary
Catalysts are used to ____ __ a reaction to increase the rate
at which a product is made or to make a process ________.
They are not normally ___ __ in a reaction and they are
reaction-specific (i.e. different reactions need _________
catalysts).
Words – different, speed up, used up, cheaper

62. 04/25/16
Rate of reaction graph v1Rate of reaction graph v1
Time taken
for reaction
to complete
Temperature/
concentration
Reaction takes a
long time here
Reaction is
quicker
here

63. 04/25/16
Rate of reaction graph v2Rate of reaction graph v2
Amount of
product
formed/
amount of
reactant used
up
Time
Slower reaction
Fast rate
of reaction
here
Slower rate of reaction here
due to reactants being used up
Rate of reaction = amount of product formed/reactant used
up

64. 04/25/16
ElectrolysisElectrolysis
+
+
+
+
-
-
-
-
Positive
electrode
Cu2+
Cu2+
Cu2+
Negative
electrode
Cl-
Cl-
Cl-
Solution
containing
copper and
chloride ions

65. 04/25/16
ElectrolysisElectrolysis
Electrolysis is used to separate a metal from its compound.
= chloride ion
= copper ion
When we electrolysed
copper chloride the _____
chloride ions moved to the
______ electrode and the
______ copper ions moved
to the ______ electrode –
OPPOSITES ATTRACT!!!

66. 04/25/16
Electrolysis equationsElectrolysis equations
We need to be able to write “half equations” to show what
happens during electrolysis (e.g. for copper chloride):
2 2
2
At the negative electrode the
positive ions GAIN electrons to
become neutral copper ATOMS. The
half equation is:
Cu2+
+ e-
Cu
At the positive electrode the
negative ions LOSE electrons to
become neutral chlorine
MOLECULES. The half equation is:
Cl-
- e-
Cl2

67. 04/25/16
Purifying CopperPurifying Copper
+
+
+
+
-
-
-
-
Solution
containing
copper ions
Impure
copper
Cu2+
Cu2+
Cu2+
Pure copper
At the positive electrode:
Cu(s) Cu2+
(aq) + 2e-
At the negative electrode:
Cu2+
(aq) + 2e-
Cu(s)

68. 04/25/16
Electrolysis of brineElectrolysis of brine
Positive
electrode
Negative
electrode
Sodium
chloride (brine)
NaCl(aq)
Sodium hydroxide
(NaOH(aq))
Sodium chloride (salt) is made of an alkali metal and a
halogen. When it’s dissolved we call the solution “brine”,
and we can electrolyse it to produce 3 things…
Chlorine gas (Cl2) Hydrogen gas (H2)

69. 04/25/16
Universal Indicator and the pH scaleUniversal Indicator and the pH scale
Strong acid Strong alkali
Neutral
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Universal Indicator is a mixture of liquids that will produce a
range of colours to show how strong the acid or alkali is:
Stomach acid Lemon juice Water Soap Oven cleanerBaking powder
An acid contains hydrogen ions, H+
An alkali contains hydroxide ions, OH-

70. 04/25/16
Neutralisation reactionsNeutralisation reactions
When acids and alkalis react together they will NEUTRALISE
each other:
OHNa
Sodium hydroxide
ClH
Hydrochloric acid
The sodium “replaces”
the hydrogen from HCl
ClNa
Sodium chloride
H2O
Water
General equation: H+
(aq) + OH-
(aq) H2O(l)

71. 04/25/16
Making saltsMaking salts
Whenever an acid and alkali neutralise each other we are left
with a salt, like a chloride or a sulphate. Complete the
following table:
Hydrochloric
acid
Sulphuric acid Nitric acid
Sodium
hydroxide
Sodium chloride +
water
Potassium
hydroxide
Potassium
sulphate + water
Calcium
hydroxide
Calcium nitrate +
water

72. 04/25/16
Making SaltsMaking Salts
Soluble salts can be made from acids by reacting them with:
1) Metals, e.g.
Zn + 2HCl ZnCl2 + H2
2) Insoluble bases, e.g.
CuO + 2HCl CuCl2 + H20
3) Alkalis (alkali = a “soluble base”), e.g.
NaOH + HCl NaCl + H20
Salts can be made from these solutions by crystallizing them.

73. 04/25/16
Ammonium saltsAmmonium salts
Guten tag again. When ammonia dissolves
in water it produces an alkaline solution:
NH3 + H20 NH4OH
This solution can be used to make fertilisers.
Very useful!