Chlorine and its compounds are discussed. Chlorine can be prepared in the laboratory by reacting concentrated hydrochloric acid with manganese(IV) oxide or potassium manganate(VII). Chlorine is a greenish-yellow gas that is denser than air and acts as a strong oxidizing agent and bleach. It reacts with many metals and non-metals to form chlorides. Common uses of chlorine include water disinfection and manufacturing of bleaches, plastics and pesticides.

1. Chlorine and its Compounds
Chlorine and its Compounds
Charles Kidega
Kidegalize Network
 es.gulu1910@gmail.com
 +256(0)702816081

2. Introduction to chlorine
Chlorine (symbol Cl) is a greenish-yellow
gas at RT and does not exist as free
element but in a combined state as
chlorides.
It has an electronic arrangement
2:8:7 and belongs to the halogen
group or Group VII of the Periodic
Table.

3. Laboratory preparation
• Preparation of chlorine from
manganese(IV) oxide
Concentrated hydrochloric acid from a
tap funnel is added onto manganese(IV)
oxide in a round bottomed flask fitted
with a delivery tube. The mixture is
heated and bubbles are observed.

4. Chlorine is produced according to the
equation.
MnO2(s) + 4HCl (l) MnCl2(aq) + H2O(l) + Cl2(g)
The gas is passed through a wash bottle
containing water to remove hydrogen
chloride gas and through another wash
bottle containing concentrated sulphuric
acid

5. to dry the gas which is then collected
by downward delivery because the gas
is denser than air.

6. Experimental set up
heat
water concentrated sulpuric
acid
chlorine
manganese(IV)
oxide
clamp
concentrated hydrochloric acid

7. • Preparation of chlorine from
potassium manganate(VII)
Add concentrated hydrochloric acid
from a tap funnel onto solid potassium
manganate(VII) in a flat bottomed flask
fitted with a delivery tube.
Chlorine gas is produced at room
temperature according to the equation

8. 16HCl(l) + 2KMnO4(s)
2KCl(aq) +2MnCl2(aq) + 8H2O(l) + 5Cl2(g)
Pass chlorine gas through water in a
wash bottle to remove hydrogen
chloride gas and pass through
concentrated sulphuric acid to dry it.
Collect the dry gas by doward delivery

9. Experimental set up
potassium
manganate(VII)
water concentrated sulphuric
acid
chlorine
tap
concentrated hydrochloric acid

10. Remember: Chlorine turns damp blue
litmus paper red and blue litmus
solution colourless.
This is the test for chlorine.

11. Physical properties of chlorine
• It is a greenish yellow gas.
• It has a chocking, unpleasant and
irritating smell.
• It is denser than air.
• It is poisonous if inhaled.

12. Chemical reactions of chlorine
1. Reaction with water
Chlorine dissolves in water and react
with it forming hypochlorus acid and
hydrochloric acid.
H2O(l) +Cl2(g) HCl(aq) + HOCl(aq)
The solution formed turns damp blue
litmus red and coloured flower
colourless.

13. This is because chlorine bleaches the
colour of most dyes.
The bleaching action is due to
Hypochlorous acid/chloric(I) acid.
The Hypochlorous acid is very unstable
and so readily gives up its oxygen to
the dye to form a colorless compound.

14. dye + HOCl(aq) HCl(aq) + (dye + O2(g))
When chlorine water (HCl/HOCl mixture) is
exposed to sunlight, oxygen is formed.
2Cl2(g) + 2H2O(l) 4HCl(aq)+ O2(g)
The yellow chlorine water turns colorless.
This is due to the decomposition of
hypochlorous acid to form oxygen.

15. Experimental set up
Oxygen

16. 2. Reaction with metals
• Heated sodium, magnesium (white flame)
and aluminium reacts with chlorine to
form white solids.
2Na(s) + Cl2(g) 2NaCl(s)
Mg(s) + Cl2(g) MgCl2(s)
2Al(s) + 3Cl2(g) 2AlCl3(s)

17. • Heated iron reacts with dry chlorine
to form black solid, iron(III) chloride.
2Fe(s) + 3Cl2(g) 2FeCl3(s)
Remember: Iron(II) chloride is not
formed because it is immediately
oxidized to iron(III) chloride by
chlorine.

18. Experimental set up
anhydrous
calcium chloride
Iron(III) chloride

19. • Heated dutch metal (an alloy of
copper and zinc) burns in chlorine
spontaneously with a green flame to
form copper(II) chloride and a little
zinc chloride.
Cu(s) + Cl2(g) CuCl2(s)
Zn(s) + Cl2(g) ZnCl2(s)

20. 3. Reaction with non-metals
• Chlorine reacts with limited ammonia to
form nitrogen and hydrogen chloride.
2NH3(g) + 3Cl2(g) N2(g) + 6HCl(g)
It reacts with excess ammonia to form
nitrogen and ammonium chloride.

21. 8NH3(g) + 3Cl2(g) N2(g) + 6NH4Cl(s)
• Chlorine oxidizes hydrogen sulphide
to sulphur and it is reduced to
hydrogen chloride.
H2S(g) + Cl2(g) S(S) + 2HCl(g)

22. • When chlorine is bubbled into molten
sulphur, a red liquid of disulphur
chloride is formed.
2S(l) + Cl2 (g) S2Cl2(l)
• Chlorine reacts with hydrogen to
form fumes of hydrogen chloride gas.
H2(g) +Cl2(g) 2HCl(g)

23. • In limited chlorine, phosphorous reacts
to form phosphorous(III) chloride.
P4(s) + 6Cl2(g) 4PCl3(g)
In excess chlorine, phosphorous
reacts to form phosphorus(V) chloride
P4(s) + 10Cl2(g) 4PCl5(g)

24. • When warm turpentine (C10H16) is
dropped into a gas jar of chlorine, red
flash is observed accompanied by a
violent reaction and black solid
particles are formed.
C10H16(l) + 8Cl2(s) 10C(s) + 16HCl(g)

25. 4. Reaction with alkali
• Chlorine reacts with cold sodium
hydroxide solution to form sodium
hypochlorite and sodium chloride.
2NaOH(aq) + Cl2(g) NaCl(aq) + NaOCl(aq) + H2O(l)
Colourless solution turns pale yellow.

26. • Chlorine reacts with hot
concentrated sodium hydroxide
solution to form sodium chlorate
and sodium chloride solution.
6NaOH(aq) + 3Cl2(g) 5NaCl(aq) + NaClO3(aq) + 3H2O(l)

27. 5. Reaction with iron(II) ions
Chlorine oxidizes iron(II) ions to iron(III)
ions. Green solution turns brown.
2Fe2+(aq) + Cl2(g) 2Fe3+(aq) + 2Cl-(aq)

28. 6. Reaction with potassium bromide
and potassium iodide.
Chlorine displaces bromine from its
aqueous solution forming potassium
chloride and bromine.
Cl2(g) + 2Br-(aq) 2Cl-(aq) + Br2(l)
The colourless solution turns red.

29. Chlorine also displaces iodine from its
aqueous solution forming potassium
chloride and iodine.
Cl2(g) + 2I-(aq) 2Cl-(aq) + I2(s)
The colourless solution turns dark
brown and black solid is formed.
This is because chlorine is a stronger
oxidizing agent than bromine and iodine.

30. Uses of chlorine
• Disinfection during water treatment.
• Manufacture of DDT.
• Making bleaching agents.
• Bleaching cotton and wood palp.
• Making plastics.
• Manufacture of chloroform.

31. Knowledge Check 1
Qn.1(UNEB 1996/P1/26)
Chlorine can be prepared in the laboratory by
reacting
A. sodium chloride and concentrated ethanol acid.
B. potassium chlorate and concentrated sulphuric
acid.
C. sodium chloride and concentrated sulphuric
acid.
D. potassium permanganate and concentrated
hydrochloric acid.

32. Qn.2(UNEB 2001/P1/9)
The best reason for including water in the
laboratory preparation of chlorine is to
A. remove chlorine gas.
B. cool chlorine gas.
C. cool hydrogen chloride gas.
D. remove hydrogen chloride gas.

33. Qn.3(UNEB 2003/P1/39)
Chlorine dissolves in cold aqueous solution
of sodium hydroxide to produce the
following substance.
A. Sodium chlorate.
B. Sodium chloride.
C. Sodium chlorite.
D. Sodium hydrogenchloride.

34. Qn.4(UNEB 2009/P1/21)
Which one of the following substances will
not oxidise concentrated hydrochloric acid
to chlorine?
A. Potassium manganate (VII).
B. Manganese (IV) oxide.
C. Lead (IV) oxide.
D. Lead (II) oxide.

35. Qn.5(UNEB 2011/P1/7)
Which one of the following substances
are components of chlorine water?
A. Chlorine and water
B. Hydrochloric acid
C. Hydrochloric acid and chlorine
D. Hypochlorous acid and water

36. Qn.6(UNEB 1987/P1/21)
Chlorine was exposed to sunlight as
shown in the diagram below.

37. The gas collected in the test tube was
A. Chlorine
B. Hydrogen chloride
C. Oxygen
D. Hydrogen

38. Qn.7(UNEB 2011/P1/28)
Which one of the following gases is
evolved when a mixture of concentrated
sulphuric acid, manganese(IV) oxide and
sodium cloride is warmed?
A. Hydrogen chloride B. Sulphur dioxide
C. Chlorine D. Oxygen

39. Qn.8(UNEB 1997/P1/4)
The gas formed when chlorine water is
exposed to sunlight is
A. oxygen.
B. hydrogen.
C. chlorine.
D. hydrogen chloride.

40. Qn.9(UNEB 2012/P2/14)
(a)Describe how a pure dry sample of
chlorine can be prepared in the
laboratory starting from potassium
manganate(VII) (NO diagram is
required, but your description must
include conditions and equation for
the reaction).

41. (b) State what would be observd and write
equation(s) for the reaction(s) that would
occur if
(i) chlorine was bubbled into an aqueous
sodium hydroxide.
(ii) burning magnesium was lowered into a
jar of dry chlorine.
(iii) Chlorine was passed through a solutin of
potassium iodide.
(c) State one use of chlorine.

42. Qn.10(UNEB 2002/P2/9)
(a) Chlorine can be prepared from concentrated
hydrochloric acid.
(i) Name a substance that can react with
hydrochloric acid to produce chlorine.
(ii) Write equation for the reaction.
(b) Chlorine gas was passed through cold dilute
sodium hydroxide solution.
(i) State what was observed.
(ii) Write equation for the reaction that took
place.

43. Qn.11(UNEB 2014/P2/13)
(a) Chlorine can be prepared in the
laboratory using potassium
manganate(VII) , KMnO4.
(i) Name one substance that reacts
with potassium manganate (VII)
to produce chlorine.

44. (ii) State the condition for the
reaction.
(iii) Write an equation for the reaction
leading to the formation of
chlorine.
(b) Damp blue litmus paper was dropped in
a gas jar containing chlorine. State
what was observed and explain your
observation(s).

45. (c) A boiling tube filled with chlorine
water was inverted into a beaker
containing chlorine water and exposed
to sunlight for sometime.
(i) State what was observed.
(ii) Explain with the aid of
equation(s), your observation(s)
in c(i).

46. Qn.12(UNEB 1999/P2/14)
(a) (i) Describe with the aid of a well-
labelled diagram how a dry sample
of chlorine can be prepared in the
laboratory.
(ii) Write an equation for the
reaction that took place.
(iii) State any three uses of chlorine.

47. (b) State with the aid of equations,
what would be observed if chlorine
was added to
(i) iron(II) chloride solution,
(ii) potassium iodide solution.
(c) Burning sodium was plunged into a
jar of chlorine.

48. Qn.13(UNEB 1990/P2/5)
The diagram in Fig 1 shows a set up of
the apparatus for the laboratory
preparation of dry chlorine from
hydrochloric acid.

49. chlorine

50. (a) (i) Name substances A, B and C.
(ii) State the role of substance B.
(b) State the conditions for the
reaction.
(c) Write equation for the reaction.

51. Qn.14(UNEB 1997/P2/2)
During the preparation of chlorine in the
laboratory, the gas may be passed
through water and concentrated
sulphuric acid before collection.
(a) State the use of water and
concentrated sulphuric acid.

52. (b) Chlorine is a bleaching agent when in
the presence of water.
(i) Write an equation for the
reaction between chlorine and
water.
(ii) Using equations explain the
bleaching action of chlorine.

53. (c) (i) State what would be observed if
chlorine was bubbled through a
solution of iron(II) sulphate
solution.
(ii) Write an ionic equation for the
reaction between chlorine and
iron (II) ions.

54. Qn.15(UNEB 2013/P2/11)
(a) Describe how a pure dry sample of
chlorine can be prepared in the
laboratory from potassium
manganate (VII) crystals (Your
answer should include a well labeled
diagram and equation for the
reaction)

55. (b) State what would be observed if
chlorine was bubbled through a:
(i) blue litmus solution
(ii) potassium bromide solution
(iii) solution of iron (II) ions

56. (c)Write equation for the reaction in
b(ii) and (iii).
(d) Write equation for the reaction
between chlorine and
(i) heated iron,
(ii) cold dilute sodium hydroxide
solution.

57. Qn.16(UNEB 1988/P2/9)
(a) The diagram below shows a
arrangement of the apparatus for
the laboratory preparation of
chlorine.

59. (i) Identify liquids P and Q.
(ii)What is the function of liquid R?
(iii)Why is chlorine collected as
shown?
(b) Write an equation for the reaction
between chlorine and aqueous iron(II)
chloride.
(c) State one use of chlorine.

60. Hydrogen chloride
Preparation of hydrogen chloride
Experimental set up
concentrated sulphuric acid
concentrated sulphuric acid
sodium chloride
hydrogen chloride

61. Concentrated sulphuric acid in a tap
funnel is added to the sodium chloride
in a flat bottomed flask fitted with a
cork carrying delivery tube.
The reaction occurs at room
temperature and bubbles of the gas
occurs. The gas is produced according
to the equation.

62. NaCl(s) + H2SO4(l) HCl(g) + NaHSO4(s)
The gas is passed through a wash
bottle containing concentrated
sulphuric acid to dry it and collected by
downward delivery since it is denser
than air.
Remember: When dilute sulphuric acid
is used, heat is applied.

63. Physical properties
• It has a pungent chocking smell.
• It is very soluble in water.
• It is denser than air.
• It is a colorless gas, but in damp air,
it forms white fumes (misty).
• It soluble in methylbenzene.

64. Chemical properties
• Hydrogen chloride gas turns damp
blue litmus paper red.
• It forms dense white fumes with
ammonia (Test for hydrogen chloride).
NH3(g) + HCl(g) NH4Cl(s)
• Dry hydrogen chloride gas reacts
with heated metals to form
anhydrous metal chlorides (white

65. solids) and hydrogen gas.
Mg(s) + 2HCl(g) MgCl2(s) + H2(g)
Zn(s) + 2HCl(g) ZnCl2(s) + H2(g)
Fe(s) + 2HCl(g) FeCl2(s) + H2(g)

66. Experimental set up
dry
hydrogen chloride
metal e.g. Fe, Al, Mg
metal chloride
hydrogen
water
heat
clamp

67. • It forms a white precipitate with
silver nitrate solution.
AgNO3(aq) + HCl(g) AgCl(s) + HNO3(aq)
The precipitate dissolves in ammonia
solution forming a colourless solution.
AgCl(s) + NH3(aq) Ag(NH3)2
+(aq) + Cl-(aq)

68. Remember: In aqueous solution,
hydrogen chloride ionizes into hydrogen
ions and chlorides because water is a
polar solvent whereas in methylbenzene
hydrogen chloride remains in molecular
form and no hydrogen ions are formed
because methylbenzene is a non-polar
solvent.

69. Therefore, in methylbenzene, hydrogen
chloride
• has no effect on litmus paper.
• does not conduct electricity.
• does not react with carbonates and
hydrogencarbonates to form carbon
dioxide.
• does not liberate hydrogen gas with
metals.

70. Knowledge Check 2
Qn.1(UNEB 1988/P1/2)
A solution of hydrogen chloride in dry
methyl benzene will
A. form sodium chloride and water with
sodium hydroxide.
B. liberate carbon dioxide with sodium
hydrogen carbonate.
C. liberate hydrogen with magnesium.
D. not conduct an electric current.

71. Qn.2(UNEB 2013/P1/20)
Which one of the following is not a property
of hydrogen chloride gas?
A. It forms white precipitate with silver
nitrate.
B. It turns moist blue litmus paper red.
C. It forms white fumes with ammonia gas.
D. It bleaches coloured flowers.

72. Qn.3(UNEB 2014/P1/4)
Which one of the following substances will
form white fumes with hydrogen chloride?
A. Concentrated sodium hydroxide
solution.
B. Concentrated nitric acid.
C. Concentrated sulphuric acid.
D. Concentrated ammonia solution.

73. Qn.4(UNEB 1991/P2/14)
(a) Draw a well-labelled diagram to
show how a sample of dry hydrogen
chloride can be prepared.
(b) Dry hydrogen chloride gas was
passed over heated iron fillings.
Write an equation for the reaction
that took place.

74. (c) The solid product in (b) was
dissolved in water and aqueous sodium
chloride added to the resultant
solution dropwise until in excess.
(i) State what was observed.
(ii) Write equation for the reaction.

75. (d) Chlorine gas was passed through a
solution of the product in (b).
(i) State what was observed.
(ii) Write an ionic equation for the
reaction.

76. (e) Name one reagent that can be used
to test for
(i) the cation formed in (d).
(ii) the anion formed in (d).
In each cases state what is observed
when the reagent you have named is
used.

77. Qn.5(UNEB 2003/P2/12)
(a) Write equation to show how
hydrogen chloride can be prepared
from sodium chloride.
(b) Draw a labelled diagram to show how
aqueous hydrogen chloride can be
prepared in the laboratory.

78. (c) State what would be observed and
write equation for the reaction that
would take place when aqueous
hydrogen chloride is reacted with:
(i) solid calcium carbonate.
(ii) silver nitrate solution.
(iii) magnesium.
(d) State why aqueous hydrogen chloride
does not react with copper.

79. Qn.6(UNEB 1998/P2/11)
(a) Describe how a dry sample of hydrogen
chloride can be prepared from a named
chloride. (No diagram is required). Your
answer should include the following:
- Conditions for the reaction.
- Name of the drying agent.
- Method of collection.
- Equation for the reaction.

80. (b) Name the substance that is formed
when hydrogen chloride is passed
through water.
(c) (i) Name one reagent that can be used
to test for the presence of chloride
ions in solution.
(ii) State what would be observed if the
reagent was added to chloride
solution.

81. (d) Write an ionic equation to show the
reaction between aqueous hydrogen
chloride and calcium hydrogen
carbonate solution.

82. Qn.7(UNEB 2018/P2/12)
(a) Explain how a dry sample of hydrogen
chloride can be prepared from sodium
chloride. (Your answer should include
equation, but no diagram is required)
(b) State what would be observed and write
equation for the reaction that would take
place if hydrogen chloride was passed.
(i) over strongly heated iron wire
(ii) through aqueous silver nitrate

83. Qn.8(UNEB 2017/P2/6)
(a) Hydrogen chloride can be produced
from potassium chloride
(i) Name another reagent that is
used with potassium chloride to
produce hydrogen chloride.
(ii) Write an equation for the
reaction leading to the formation
of hydrogen chloride.

84. (b) Write an equation for the reaction
between hydrogen chloride and
(i) silver nitrate solution.
(ii) iron in the presence of water.

85. Qn.9(UNEB 2016/P2/7)
State what would be observed and
write ionic equation for the reaction
that would take place if hydrogen
chloride was bubbled through aqueous
(a) sodium hydrogen carbonate.
(b) silver nitrate.

86. Qn.10(UNEB 2015/P2/12)
(a) Briefly describe how a dry sample of
hydrogen chloride can be prepared in the
laboratory. (Diagram is not required)
(b) Hydrogen chloride was bubbled through a
solution of lead(II) nitrate
(i) State what was observed and explain
your answer.
(ii) Write an equation for the reaction that
took place.

87. Hydrochloric acid
Preparation of hydrochloric acid
Experimental set up

88. Concentrated sulphuric acid from a tap
funnel is added to sodium chloride in a flask
fitted with a delivery tube.
The gas produced is passed through a
delivery tube connected to a filter funnel
immersed in water.
HCl(g) H+(aq) + Cl-(aq)
The rim of the funnel is just immersed to
prevent sucking back of water.
H2O

89. Reactions of hydrochloric acid
• It turns blue litmus paper red.
• It liberates carbon dioxide from
carbonates and hydrogencarbonates.
NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)
CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)
• It reacts with metals above copper in the
reactivity series producing hydrogen gas.

90. Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)
• It reacts with bases and alkalis to
form salts and water only.
NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)
CuO(s) + 2HCl(aq) CuCl2(aq) + H2O(l)

91. Test for chloride ions
Reagent 1: Dilute nitric acid followed
by silver nitrate solution, then ammonia
solution.
Observation: White precipitate,
dissolves in ammonia solution forming
colourless solution.

92. Reagent 2: Dilute nitric acid followed
by lead(II) nitrate solution and warm.
Observation: White precipitate soluble
on warming and reforms on cooling.
Pb2+(aq) + 2Cl-(aq) PbCl2(s)

93. Reagent 3: Concentrated sulphuric
acid added onto solid chloride in dry
test tube.
Observation: Bubbles of misty fumes
which turn damp blue litmus paper red
and form dense white fumes with
ammonia gas.

94. Knowledge Check 3
Qn. 1 (UNEB 1987/P1/13)
Which one of the following anions will
react with silver nitrate solution to
give a white precipitate soluble in
excess aqueous ammonia?
A. Cl- B. NO3
-
C. SO4
2- D. CO3
2-

95. Qn. 2 (UNEB 2002/P1/7)
Which one of the following anions does
not form a precipitate with Pb2+(aq)?
A. CO3
2-(aq) B. OH-(aq)
C. NO3
-(aq) D. SO4
2-(aq)

96. Qn. 3 (UNEB 2002/P1/8)
Which one of the following ions reacts
with Cl- to form a precipitate which
dissolves on heating ?
A. Cu2+ (aq) B. Fe2+(aq)
C. Pb2+(aq) D. Ca2+(aq)

97. Qn. 4 (UNEB 2002/P1/9)
A colourless solution reacts with dilute
hydrochloric acid to give a white
precipitate. The white precipitate
dissolves in warm water. The colourless
solution is
A. zinc chloride. B. lead nitrate.
C. magnesium sulphate.
D. sodium carbonate

98. Qn. 5(UNEB 2007/P1/4)
Which one of the following salts will not
form a precipitate with lead(II) ions?
A. Sodium carbonate
B. Calcium nitrate
C. Ammonium chloride
D. Potassium sulphate