The document describes several experiments involving qualitative analysis of salts and acids. Salt X is identified as lead(II) carbonate from its reaction to produce solid Y and carbon dioxide gas when heated. Solution W is found to contain nitrate ions, identified through a test producing a brown ring with sulfuric acid and iron(II) sulfate. A precipitation reaction between solutions of lead nitrate and potassium iodide is used to calculate the mass of yellow precipitate formed. Strong acids such as hydrochloric acid and sulfuric acid are described as reacting with bases to produce salts and water, with metals to produce salts and hydrogen gas, and with carbonates to produce salts, carbon dioxide, and water. The role of water in

1. CHAPTER 6
5 Diagram 5 shows a flow chart for the qualitative analysis of salt X. The white colour of salt X is
heated strongly to produce solid Y and carbon dioxide gas. Solid Y shows brown colour when
hot and yellow colour when cold.
a) State the name of salt X.
………………………………………………………………………………………………………………………………….
b) Carbon dioxide gas reacts with lime water to form precipitate V.
Write a balanced chemical equation for the reaction.
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c) i) State the anion presents in the aqeuous solution W.
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ii) Briefly describe how would your verify the anion mentioned in 5(c)(i).
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d) 50 cm3
of 0.5 mol dm-3
aqueous solution W reacts with 50 cm3 of 0.5 mol dm-3 potassium
iodide solution to form a yellow precipitate. Calculate the mass of precipitate formed.
[Relative atomic mass : Pb = 207, I = 127]

2. 10 Table 10 shows the set-up of apparatus to investigate the role of water in showing the
properties of acid.
a) Based on the information in Table 10, name a suitable substance that can be sued as
solvent X and solvent Y. Explain why the observations of Experiment I and Experiment II
are different.
[6 marks]
b) By using an example of strong acid, explain one chemical property of an acid.
Include the chemical equations in your explanation.
[4 marks]
c) Describe how to prepare 250 cm3
of 1.0 mol dm-3
sodium hydroxide solution starting from
solid sodium hydroxide in the school laboratory.
Include the following in your description :
 The materials and apparatus needed
 The calculation involved
[Relative atomic mass : H = 1, O = 16, Na = 23]
 The steps involved in the preparation
[4 marks]

3. 5 Diagram 5.1 shows the set-up of apparatus to prepare two solutions where hydrogen chloride
gas is dissolved in solvent K and solvent L. A piece of red litmus paper is dipped into each
beaker.
Table 5 shows the results of an experiment above.
a) Suggest a substance for solvents K and L.
i) Solvent K
…………………………………………………………………………………………………………………………
ii) Solvent L
…………………………………………………………………………………………………………………………
b) Explain why the moist blue litmus paper remains unchanged in experiment that used
solvent K.
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………………………………………………………………………………………………………………………………...

4. c) Diagram 5.2 shows two beakers S and T filled with sulphuric acids S and T, of different
concentrations.
i) What is meant by acid?
…………………………………………………………………………………………………………………………
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[1 marks]
ii) Explain why suphuric acid is a strong acid?
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[1 marks]
iii) Solutions S and T have different pH values. Which solution gives a lower pH value?
Explain why.
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[2 marks]

5. d) 25 cm3
of 0.1 mol dm-3
potassium hydroxide solution is put in a conical flask. Then a few
drops of phenolphthalein are added and hence titrated with solution S.
i) Write the chemical equation for the reaction.
…………………………………………………………………………………………………………………………
[2 marks]
ii) Calculate the volume of sulphuric acid used.
[2 marks]

6. 8 Three series of tests, I, II and III are carried out on an 𝑋 chloride solution as shown in the
following flow chart.
a) i) List all the ions that can be identified from test I.
…………………………………………………………………………………………………………………………
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[3 marks]
ii) Name the X chloride solution and write its chemical formula.
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[2 marks]
b) Based on the test III,
i) Name the type of reaction
…………………………………………………………………………………………………………………………
[1 mark]
c) i) Write the chemical equation when solution chloride 𝑋 react with excess NaOH.
…………………………………………………………………………………………………………………………
[1 mark]
ii) From the chemical equation in (c)(i), calculate mass of white solid formed when
10 cm3
of 0.1 mol dm-3
𝑋 chloride solution react with excess NaOH.
[1 mark]

7. d) X chloride solution is contaminated by sulphate ion, SO42-. Compare both ions, in term
of :
 Steps to identify the ion in the lab
 Observation
 Name and chemical formula of precipitate that formed
 Ionic equation
 Name of reaction
[1 mark]

8. ANSWERS
5 Diagram 5 shows a flow chart for the qualitative analysis of salt X. The white colour of salt X is
heated strongly to produce solid Y and carbon dioxide gas. Solid Y shows
brown colour when hot and yellow colour when cold.
a) State the name of salt X.
Lead(II) carbonate
b) Carbon dioxide gas reacts with lime water (Ca(OH)2)to form precipitate V.
Write a balanced chemical equation for the reaction.
CO2 + Ca(OH)2 → CaCO3 + H2O
 Correct chemical formula of reactants and products – 1m
 Balanced chemical equation – 1m
c) i) State the anion presents in the aqeuous solution W.
Nitrate ion // NO3
-
Pb2+
HNO3

9. ii) Briefly describe how would your verify the anion mentioned in 5(c)(i).
Describe the anion test for nitrate ion, NO3
-
1. 2 cm3
of dilute sulphuric acid, H2SO4, is added to 2 cm3
solution W followed
by 2 cm3
of iron(II) sulphate solution, FeSO4 and the mixture is shaken.
2. The test tube is slanted and held with a test tube holder, a few drops of
concentrated sulphuric acid, H2SO4 are added along the wall of the test tube
and is held upright.
3. A brown ring is formed. Anion present is nitrate ion.
d) 50 cm3
of 0.5 mol dm-3
aqueous solution W reacts with 50 cm3
of 0.5 mol dm-3
potassium
iodide solution to form a yellow precipitate. Calculate the mass of precipitate formed.
[Relative atomic mass : Pb = 207, I = 127]
Chemical equation :
Number of moles of Pb(NO3)2 =
. ×
= 0.025 mol
Number of moles of KI =
. ×
= 0.025 mol
Mole ratio :
2 mol of KI produce 1 mol of PbI2
0.025 mol of KI produce 0.0125 mol of PbI2
Mass of PbI2 = 0.0125 × [207 + 2(127)] = 5.7625 g
anion test for nitrate ion, NO3
1. Add dilute H2SO4
2. Add freshly made FeSO4
3. (Slant test tube) Add few
drops of concentrated
H2SO4 along the wall of test
tube
4. Brown ring = Nitrate ion

10. 10 Table 10 shows the set-up of apparatus to investigate the role of water in showing the
properties of acid.
a) Based on the information in Table 10, name a suitable substance that can be sued as
solvent X and solvent Y. Explain why the observations of Experiment I and Experiment II
are different.
Experiment I
1. Solvent X: Water
2. Hydrogen chloride gas ionises in water to produce hydrogen ions and chloride
ions.
3. The presence of hydrogen ions causes the hydrochloric acid to react with
magnesium to produce hydrogen gas.
Experiment II
1. Solvent Y : Propanone // methylbenzene // trichloromethane //
tetrachloromethane
2. In organic solvent, hydrogen chloride still exists as molecules.
3. Without the presence of hydrogen ion, the reaction does not occur
[6 marks]

11. b) By using an example of strong acid, explain one chemical property of an acid.
Include the chemical equations in your explanation.
1. Acid reacts with a base or alkali to produce salt and water.
Hydrochloric acid reacts with sodium hydroxide solution to produce sodium
chloride and water.
HCl + NaOH → NaCl + H2O
2. Acid reacts with a reactive metal to produce salt and hydrogen gas.
Nitric acid reacts with magnesium to produce magnesium nitrate and hydrogen
gas.
2HNO3 + Mg → Mg(NO3)2 + H2
3. Acid reacts with a metal carbonate to produce salt, carbon dioxide gas and
water.
Sulphuric acid reacts with calcium carbonate to produce calcium sulphate, carbon
dioxide gas and water.
H2SO4 + CaCO3 → CaSO4 + CO2 + H2O
Note : Example of strong acid: HCl, HNO3, H2SO4
[4 marks]
c) Describe how to prepare 250 cm3
of 1.0 mol dm-3
sodium hydroxide solution starting
from solid sodium hydroxide in the school laboratory.
Include the following in your description :
 The materials and apparatus needed
Materials : Solid sodium hydroxide and distilled water
Apparatus : 250 cm3
volumetric flask, 50 cm3
beaker, weighing bottle, electronic
balance, glass rod and filter funnel
 The calculation involved :
[Relative atomic mass : H = 1, O = 16, Na = 23]
Number of moles of NaOH
=
𝑴𝑽
𝟏𝟎𝟎𝟎
=
𝟏 × 𝟐𝟓𝟎
𝟏𝟎𝟎𝟎
= 𝟎. 𝟐𝟓 𝒎𝒐𝒍
Mass of NaOH needed = 0.25 × [23 + 16 + 1] = 10 g
 The steps involved in the preparation
Steps :
1. 10.0 g of solid sodium hydroxide is weighed in a dry weighing bottle.
2. Solid sodium hydroxide is transferred into a beaker containing 25 cm3 of distilled
water and the mixture is stirred to dissolve the solid.
3. The solution from the beaker is then carefully poured into a 250 cm3 volumetric
flask through a filter funnel.
4. The weighing bottle and the beaker are rinsed with a small amount of distilled
water and poured into the volumetric flask.
5. Distilled water is poured into the volumetric flask until the calibration mark.
6. The volumetric flask is then closed with a stopper and inverted a few times to get
homogenous solution
[4 marks]

12. 5 Diagram 5.1 shows the set-up of apparatus to prepare two solutions where hydrogen chloride
gas is dissolved in solvent K and solvent L. A piece of red litmus paper is dipped into each
beaker.
Table 5 shows the results of an experiment above.
a) Suggest a substance for solvents K and L.
i) Solvent K
Methylbenzene // [any organic solvent]
ii) Solvent L
Water
b) Explain why the moist blue litmus paper remains unchanged in experiment that used
solvent K.
There is no water present. Therefore, no hydrogen ions present / hydrogen chloride
remains as molecules.

13. c) Diagram 5.2 shows two beakers S and T filled with sulphuric acids S and T, of different
concentrations.
i) What is meant by acid?
A substance that ionises in water to produce hydrogen ion.
[1 marks]
ii) Explain why suphuric acid is a strong acid?
A substance that ionises completely in water to produce high concentration of
hydrogen ion.
[1 marks]
iii) Solutions S and T have different pH values. Which solution gives a lower pH value?
Explain why.
S. It has a higher concentration of hydrogen ions.
[2 marks]
d) 25 cm3
of 0.1 mol dm-3
potassium hydroxide solution is put in a conical flask. Then a few
drops of phenolphthalein are added and hence titrated with solution S.
i) Write the chemical equation for the reaction.
2KOH + H2SO4 → K2SO4 + 2H2O
[2 marks]
ii) Calculate the volume of sulphuric acid used.
Number of moles of KOH
=
0.1 𝑥 25
1000
= 0.0025 mole
From equation,
2 mole KOH : 1 mole H2SO4
0.0025 mole KOH : 0.00125 mole H2SO4
Volume of H2SO4
=
.
.
=0.0125 dm3
=12.5 cm3

14. [2 marks]

15. 8 Three series of tests, I, II and III are carried out on an 𝑋 chloride solution as shown in the
following flow chart.
a) i) List all the ions that can be identified from test I.
Lead ion, aluminium ion, zinc ion
[3 marks]
ii) Name the X chloride solution and write its chemical formula.
Zinc Chloride, ZnCl2
[2 marks]
b) Based on the test III,
i) Name the type of reaction
Double decomposition reaction
[1 mark]
c) i) Write the chemical equation when solution chloride 𝑋 react with excess NaOH.
ZnCl2 + 2NaOH →Zn(OH)2 + 2NaCl
[1 mark]
ii) From the chemical equation in (c)(i), calculate mass of white solid formed when
10 m3
of 0.1 mol dm-3
𝑋 chloride solution react with excess NaOH.
1 mol ZnCl2 : 1 mol Zn(OH)2
0.001 mol ZnCl2 : 0.001 mol Zn(OH)2
Mass of Zn(OH)2
= 0.001 × 99
= 0.099 g // 0.01g
[1 mark]

16. d) X chloride solution is contaminated by sulphate ion, SO42-. Compare both ions, in term
of :
 Steps to identify the ion in the lab
 Observation
 Name and chemical formula of precipitate that formed
 Ionic equation
 Name of reaction
[1 mark]