Diamond has a giant covalent structure where each carbon atom is bonded to four other carbons, giving it properties like hardness and electrical insulation. It is used in cutting, jewelry due to its brilliance, and lasers. Graphite has layers of hexagonal carbon sheets bonded by van der Waals forces, making it soft and a conductor. It is used as a lubricant, in electrodes, and pencils. Hard water contains calcium and magnesium ions that form precipitates with soap. Temporary hardness can be removed by boiling or adding washing soda while permanent hardness requires ion exchange or distillation. Carbon forms oxides, is a reducing agent, and is important in combustion, fermentation, and the carbon cycle.

1. Diamond

2. Structure
 Diamond has giant atomic structure.
 In diamond, each carbon atom uses all its four
valency electrons to form covalent bonds with
four other carbon atoms. This results into a
three dimensional giant atomic structure with
very high melting point. So diamond is the
hardest substance known on earth.
 Since carbon uses all its four valency electrons,
diamond does not conduct electricity.

4. Physical properties
 It is the hardest substance known
 It is colourless and transparent with a brilliant
appearance.
 It is denser than graphite.
 It is a poor conductor of electricity.

7. Uses
 It is used to cut glass and make tips of drilling
machines because it is very hard.
 Because of its brilliant appearance, it is used to
make jewellery.
 Because of its brightness, it is used to make
laser beams.

8. Graphite

9. Structure

10. Structure
 In graphite, each carbon atom is bonded to
three others by covalent bonds forming
hexagonal layers.
 The fourth valency electron is delocalised and is
free to move along the layers. Therefore
graphite conducts electricity along its layers.
The layers are held by weak Van der Waals
forces and can slide over each other. Therefore
graphite is soft.

11. Physical properties
 It conducts electricity.
 It is soft
 It has a density of 2.2g/
Uses of graphite:
 It is used as a lubricant since it is soft.
 It is used as electrodes in electrolysis since it is a
good conductor of electricity.
 It is used in making lead pencils.

12. Chemical properties of carbon

13. Combustion
 Carbon burns in excess oxygen to form carbon
dioxide.
 In a limited supply of oxygen, incomplete
combustion occurs and carbonmonoxide is
produced.

14. Carbon as a reducing agent
 Carbon readily removes oxygen from oxides of
zinc and other metal oxides below zinc in the
activity series and itself oxidized to
carbondioxide.

15. Carbon as a reducing agent
 Carbon also reduces concentrated nitric acid to
nitrogen dioxide and concentrated sulphuric
acid to sulphur dioxide.

16.  If steam is blown through red hot charcoal, a
mixture of carbon monoxide and hydrogen is
obtained. This mixture is called water gas.

17. Oxides of carbon

18.  Preparation

20.  Some calcium carbonate is placed into the flask
and the apparatus is assembled as shown in the
diagram above.
 Dilute hydrochloric acid is poured on to the
calcium carbonate through a dropping funnel
(or a thistle funnel) until all the calcium
carbonate is covered.
 Effervescence of a colourless gas (carbon
dioxide) occurs and it is collected over
water since it slightly soluble in it.

21.  If required dry, the gas is passed through water
to absorb any traces of hydrochloric acid. It is
then passed through concentrated sulphuric
acid to dry it.
 The gas is then collected by downward delivery
since it is denser than air.
Equation of the reaction that takes place in the
flask:

22.  In general, carbonates react with acids to form
carbon dioxide gas and water.

23.  Note:
 Dilute sulphuric acid is not used to prepare
carbon dioxide because it reacts with the
calcium carbonate to form insoluble calcium
sulphate, which prevents the acid from contact
with the calcium carbonate and the reaction
soon stops.
 Anhydrous calcium chloride may be as a drying
agent instead of sulphuric acid.

24.  If the gas is not required dry, it can be collected
over water since it is slightly soluble in water.
 Other reactions which can produce carbon
dioxide include: Combustion of hydrocarbons,
Fermentation, Respiration, Action of heat on
carbonates and hydrogen carbonates.

25.  Test for carbon dioxide:
 Carbon dioxide gas turns limewater milky.
Physical properties of carbon dioxide.
 It is a colourless, odourless, and has a sharp
pleasant taste gas.
 It is denser than air.
 It is slightly soluble in water forming a weak
carbonic acid solution. This solution turns blue
litmus paper pink showing that it is a weak acid.

26. Carbon dioxide
 Under high pressure carbon dioxide is quite
soluble and that is why it is used in fizzy
drinks such as sodas.
Chemical properties.
(a) Combustion
Carbon dioxide does not burn or support
burning.

27. Properties of carbon dioxide
(b) With magnesium.
Lower burning magnesium ribbon into a gas
jar of carbon dioxide
Observation:
 It continues to burn with sputtering
forming black specks of carbon on the
sides of the jar, together with white ash of
magnesium oxide.
2Mg(s) + CO2(g) 2MgO(s) + C(s)
.

28. (c) Reaction with calcium hydroxide solution.
When carbon dioxide is bubbled through lime water, a white
precipitate is formed due to the formation of insoluble calcium
carbonate.
Ca(OH)2(aq) + CO2(g) CaCO3(s) +H2O (l)
This is used as a test for carbon dioxide.
However, when excess carbon dioxide is bubbled through
limewater, a colourless solution is obtained due to the formation of
soluble calcium hydrogen carbonate.
CO2(g) +CaCO3(s) +H2O ) Ca(HCO3) (aq)

29. (d) Reaction with sodium hydroxide solution.
When the gas is bubbled through a fairly
concentrated sodium hydroxide solution, the
solution is observed to remain colourless at first
but a white precipitate is formed with excess
carbon dioxide.
The solution remains colourless at first due to the
formation soluble sodium carbonate.
With excess carbon dioxide, sodium hydrogen
carbonate is formed, which is just slightly soluble.

30. Uses of carbon dioxide:
•It is used in fire extinguishers since it does not
support burning and it is denser than air.
•It is used as a preservative in fizzy (aerated
drinks) e.g. sodas.
•Used as a refrigerant (especially dry ice or solid
carbon dioxide).
•Used in the manufacture of baking powder.
•Used as a food preservative e.g. in dairy
products, fruits and vegetables.

31. CARBONATES AND HYDROGEN
CARBONATES

32. Occurrence
 Potassium carbonate and sodium
carbonate occur naturally in salty lakes
e.g. L. Katwe.
 Calcium and magnesium carbonates occur
in rocks.
 Carbonates are salts derived from
carbonic acid.

33. Properties
Solubility
 All carbonates are insoluble in water
except potassium carbonate, sodium
carbonate and ammonium carbonate.
 There are only three solid hydrogen
carbonates (sodium hydrogen carbonate,
potassium hydrogen carbonate and
ammonium hydrogen carbonate) and are
all soluble in water except sodium
hydrogen carbonate which is slightly
soluble.

34. Action of heat
 Carbonates of potassium, sodium are not
decomposed by heat. However, when their
hydrated carbonates are heated, they lose
their water of crystallization e.g.
 All other metal carbonates decompose when
heated forming respective metal oxides and a
gas that turns lime water milky (carbon
dioxide)

35. Action of heat
 Ammonium carbonate sublimes when
heated to give ammonia gas, water vapour
and carbon dioxide.
 Aluminium carbonate does not exist.

36. Action of heat
Hydrogen carbonates.
 All hydrogen carbonates decompose
when heated to give the corresponding
carbonates, water vapour and carbon
dioxide e.g.

37. Reaction with acids
 Both carbonates and hydrogen carbonates
react with dilute acids to liberate carbon
dioxide gas, water and the corresponding
salt i.e.

38. Reaction with acids
 The following reactions proceed at very
slow rate and stop soon because in each
case the resulting salt is insoluble. These
salts form a coating around the carbonate
stopping any further reaction.
 Dilute nitric acid reacts with all
carbonates to produce soluble salts
(nitrates).

39. Test for carbonates and hydrogen carbonates
To the unknown solid, add a little dilute acid
e.g. nitric acid.
Observation.
 Bubbles of a colourless gas that turns
calcium hydroxide solution (lime water)
milky.
Conclusion
 This shows that a carbonate or hydrogen
carbonate is present.

40. Test for carbonates and hydrogen carbonates
To about 1-2cm3 of the solution of the
unknown add 2-3 drops of lead(II) nitrate
solution followed by dilute nitric acid.
Observation
 A white precipitate that dissolves in nitric
acid with effervescence of a colourless gas
that turns lime water milky confirms the
presence of a carbonate i.e.

41. Test for carbonates and hydrogen carbonates
 Alternatively, barium nitrate or barium
chloride can be used in place of lead(II)
nitrate.

42. Distinguishing between carbonates and hydrogen
carbonates
To about 1-2cm3 of the solution of the
unknown, add a little magnesium sulphate
solution.
Observations.
 A white precipitate shows presence of a
carbonate.
 No observable change shows
presence of a hydrogen carbonate.

43. SODIUM CARBONATE
Laboratory preparation.
 Bubble carbon dioxide gas through a
fairly concentrated solution of sodium
hydroxide. Sodium carbonate solution is
formed.
 Pass excess carbon dioxide through the
above mixture. A white precipitate of
sodium hydrogen carbonate is formed.

44. SODIUM CARBONATE
Laboratory preparation.
 Filter off the white precipitate, wash with
distilled water and dry it.
 The dry sodium hydrogen carbonate is
then heated to a constant mass. This
leaves a white powder of sodium
carbonate.

45. SODIUM CARBONATE
Commercial preparation (Solvay Process)
 A concentrated solution of sodium
chloride (brine) is slowly dropped down a
tower up which ammonia is moving.
 The brine-ammonia mixture is then made
to pass down a second tower up which
carbon dioxide is moving. Ammonium
hydrogen carbonate is formed.

46. SODIUM CARBONATE
Commercial preparation (Solvay Process)
 The ammonium hydrogen carbonate so
formed quickly reacts with excess brine to
form a white precipitate of sodium
hydrogen carbonate.
 The sodium hydrogen carbonate is then
filtered off, washed, dried and then
heated to a constant mass.

47. Uses of sodium carbonate
 In the manufacture of glass.
 It is a constituent of many dry soap
powders.
 Used in softening of water.
 Used in the manufacture of sodium
hydroxide (caustic soda).

48. Properties of sodium carbonate
 Anhydrous sodium carbonate is a white
powder while hydrated sodium carbonate
is a white crystalline solid.
 A solution of sodium carbonate turns red
litmus to blue. This is because sodium
carbonate reacts with water to form weak
carbonic acid and a strongly alkaline
sodium hydroxide.

49. Properties of sodium carbonate
 Sodium carbonate is not decomposed by
heat but if hydrated, It loses its water of
crystallization.
 Hydrated sodium carbonate is
efflorescent. When left exposed to the
atmosphere, the translucent crystal is
coated with a white powder due to loss of
water of crystallization.

50. CARBON CYCLE

51. CARBON CYCLE

52. CARBON CYCLE

53. HARD WATER
 This is the water that does not readily
form lather with soap due to presence of
dissolved calcium salts or magnesium
salts.

54. HARD WATER
How water becomes hard.
 When it rains, water passes through the
atmosphere, dissolves carbon dioxide
forming weak carbonic acid solution.
 As the acidic solution passes through the
rocks, it dissolves calcium carbonate or
magnesium carbonate from the rocks
forming calcium hydrogen carbonate or
magnesium hydrogen carbonate. This makes
water to have temporary hardness.
 If rain water passes through rocks containing
these calcium sulphate, some of them dissolve in
water causing it to be hard water .

55. HARD WATER
Action of soap on hard water.
 Soap is a sodium or potassium salt of
stearic acid. It has the simple formula
NaSt.
 Once dissolved in water, soap reacts with
the calcium or magnesium ions in hard
water to form a dirty white precipitate
called scum.

56. HARD WATER
Action of soap on hard water.
 Therefore soap will only form a stable
lather after all the calcium or magnesium
ions are removed by the reaction above.
This leads to wastage of soap.

57. TYPES OF HARD WATER
 Temporary hard water.
 Permanent hard water.
Temporary hard water
 This is the type of water that can be
softened by boiling.
 It is caused by presence of dissolved
magnesium hydrogen carbonate or
calcium hydrogen carbonate in water.

58. TYPES OF HARD WATER
Removal of temporary hardness.
Boiling
 Boiling decomposes soluble hydrogen
carbonates to insoluble carbonates that
can be removed from water as
precipitates.

59. TYPES OF HARD WATER
Removal of temporary hardness.
Addition of sodium carbonate (washing
soda).
Addition of calculated amount of calcium
hydroxide (slaked lime)

60. TYPES OF HARD WATER
Removal of temporary hardness.
Addition of aqueous ammonia.
Any other methods that remove permanent
hardness.

61. TYPES OF HARD WATER
Permanent hard water
 This is the type of hard water that cannot
be made soft by boiling.
 It is caused by the presence of dissolved
calcium sulphate or magnesium sulphate
(or chlorides of magnesium and calcium)
in the water.

62. TYPES OF HARD WATER
Removal of permanent hardness
Distillation
Addition of sodium carbonate solution
(washing soda)
 Sodium carbonate reacts with calcium
sulphate or magnesium sulphate to form
insoluble carbonates

63. TYPES OF HARD WATER
Removal of permanent hardness
Ion exchange method (permutit).
 Calcium or magnesium ions in hard water
can be exchanged with sodium ions by
using a suitable ion exchange material.
 Two common ion exchange materials are
zeolite and permutit.
 Zeolite is naturally occurring sodium aluminium
silicate and permutit is its artificial form.
 Zeolite and permutit can be simply represented
as Na2Y or Na2X.

64. TYPES OF HARD WATER
Removal of permanent hardness
Ion exchange method (permutit).
 This method can also be called double
decomposition.

65. TYPES OF HARD WATER
Removal of permanent hardness
Using detergents.
 Detergents form lather easily with hard
water.
 Their reaction does not produce scum
since the calcium and magnesium
compounds formed in this case are
soluble.
 Detergents have an advantage over
soap because they do not form scum
with hard water.

66. Activity
You are provided with three water samples X, Y and Z and
soap solution.
(a) Add 2cm3 of soap solution to water sample X,
Shake. State what is observed.
(b) Repeat the procedure for Samples Y and Z. Note
your observations.
(c) Heat about 5cm3 of samples Y and Z in a boiling tube,
allow to cool. Add 2cm3 of soap solution to the boiled
water sample Y and X, Shake. State what is observed.
1. Giving reasons, which of the water samples X, Y and Z is
(i) Temporary hard water.
(ii) Permanent hard water
(iii) Soft water.

67. ADVANTAGES OF HARD WATER
 Provide calcium which is essential for
growth of bones and teeth.
 It helps to form healthy animal shells and
eggs.
 Does not dissolve lead from lead pipes
thus can be transported using lead pipes.
 Used in brewing industry.
 Contains magnesium which is important
during photosynthesis.

68. DISADVANTAGES OF HARD WATER
 Leads to wastage of soap.
 Leaves dirty marks on clothes.
 Forms fur in kettles and pans which is a
bad conductor of heat.
 Causes boiler scale.
 Fur caused by hard water builds up scale
in boiler pipes. Boiler pipes may get
blocked causing serious accidents.

69. QUESTIONS
1(a) Name the ions that cause hardness in
water.
(b) Explain how water becomes hard.
(c) State two advantages of hard water.
(d) Write an equation to show how sodium
carbonate removes hardness from water
2. (a) Define the term allotropy.
(b) Give one example of an element other
than carbon which shows allotropy.
(c) Describe briefly the structure of graphite.

70. QUESTIONS
(d) State two differences between graphite
and diamond.
(e) Describe how you would show by a
chemical test that graphite is made up of
carbon atom.
3.Carbon dioxide is prepared in the
laboratory by action of dilute hydrochloric
acid on calcium carbonate and the gas
passed through water and finally through
concentrated sulphuric acid before it is
collected by downward delivery.

71. QUESTIONS
a) Why is the gas passed through;
i. Water
ii. concentrated sulphuric acid.
b) Which property of the gas enables it to be collected by
the above method.
c) Give reason why dilute sulphuric acid cannot not be
used to replace dilute hydrochloric acid in the above
method.
d) Draw a laboratory set up of the above method of
preparation of carbondioxide. Write the equation for the
reaction that takes place in the flask.