Salt Preparation Revision Structured Question

Hydrogen iodide is unstable, decomposes in light, fumes in moist air and can cause severe burns to skin and eyes. When hydrogen iodide is heated, it breaks down as shown in the equation:

2HI(g) → H2(g) + I2(g)

Hydrogen iodide is also very soluble in water and it dissociates fully in water to produce ions.

(a) Give the chemical formulae of the ions present when hydrogen iodide dissolves in water.


(b) In the laboratory preparation of lead(II) iodide, aqueous solution of hydrogen iodide can be used as one of the starting materials. However, it is not a good choice as a starting material because it is a very corrosive solution.

(i) Give an alternative starting material in the laboratory preparation of lead(II) iodide.


(ii) Outline the main steps in the method of preparing a pure and dry sample of lead(II) iodide in the laboratory, starting from the reagent given in (b)(i).






(a) H+, I, OH
(b) (i) KI/ NaI/ NH4I , or any other soluble iodide [1]
(ii) Add KI/NaI/ NH4I into Pb(NO3)2
Filter the mixture to obtain the precipitate (PbI2)
Wash residue with deionised water and dry between filter paper.
REJECT: Filtrate the mixture



Salt Preparation Revision MCQ Questions

1.    Which of the following does not show the appropriate reagents used for the preparation of the named salts?


2.    Which pair of substances produce a precipitate when their aqueous solutions are mixed?

A    sodium chloride and barium nitrate

B    sodium nitrate and barium chloride

C    sodium nitrate and silver nitrate

D    sodium sulfate (VI) and barium chloride

3.    Which of the following reaction produces the best yield of calcium sulfate?

A    Add dilute nitric acid to calcium carbonate, followed by dilute sulfuric acid.

B    Mixing solid calcium nitrate and solid potassium sulfate.

C    Add dilute sulfuric acid to calcium carbonate

D    Titrate aqueous calcium hydroxide with dilute sulfuric acid

4.    Which of the following substances in water is most suitable to react with dilute hydrochloric acid to prepare silver chloride?

A    Silver oxide

B    Silver metal

C    Silver nitrate

D    Silver carbonate

5.    Which of the following pairs of solutions when added together will produce an insoluble salt?

I     Magnesium fluoride and lead(II) nitrate

II   Sodium chloride and silver nitrate

III  Copper(II) sulfate and barium chloride

IV  Potassium carbonate and sodium nitrate

A    I and II only

B    I, II and III only

C    I, II and IV only

D    I, II, III and IV


1.    A

2.    D

3.    A

4.    C

5.    B

Acids and Bases Revision Structured Question

Sodium phosphate, Na3PO4, is a soluble salt, used as a water softener in washing
powders. It is made by reacting dilute phosphoric acid, H3PO4, with an alkali.
(a) (i) Give the formulae of the ions present in sodium phosphate.


(ii) Name the alkali which reacts with phosphoric acid to make sodium


(iii) Write a balanced chemical equation for this reaction.


(iv) Given solutions of phosphoric acid and alkali, a suitable indicator and
standard laboratory apparatus, explain how you would obtain crystals of
sodium phosphate.





Copper occurs naturally in the ore malachite CuCO3.Cu(OH)2. When malachite
is heated it produces copper(II) oxide, carbon dioxide and water.
Malachite can be readily converted into copper by heating it with carbon.
(b) Write a balanced chemical equation for the action of heat on malachite.



(a) (i) Na+ , PO43- [Both must be correct]
(ii) Sodium hydroxide [NaOH will NOT be accepted]
(iii) 3NaOH + H3PO4 –> Na3PO4 + 3H2O
(iv) A fixed volume of phosphoric acid is pipetted into a conical flask and a few of                   drops of methyl orange/ phenolphthalein is added. From a burette, sodium hydroxide is       added to the acid until methyl orange turns orange/phenolphthalein turns pink. The             volume of the alkali used is noted.
The experiment is repeated to achieve consistent results. In the absence of the                         indicator, add the average volume of alkali required and a fixed volume of acid used to           obtain a solution of sodium.
Warm the solution of sodium phosphate to obtain a saturated solution
Leave the solution to cool and crystals of sodium phosphate will be obtained.

(b) CuCOM3.Cu(OH)2 ⇌ 2CuO + CO2 + H2O

Acids and Bases Revision MCQ Questions

1.    Four particles are present in dilute sulfuric acid.

Which particle is present in the lowest concentration?

A    The hydroxide ion. OH (aq)

B    The hydrogen ions, H+(aq)

C    The sulfate ion. SO42-(aq)

D    The water molecule. H2O(l)

2.    The following statements about dilute sulfuric acid are all correct.

  1. A white precipitate is formed when aqueous barium chloride is added.
  2. The solution turns anhydrous copper (II) sulfate from white to blue.
  3. Addition of Universal indicator shows that the solution has a pH value of lesser than 7.0
  4. The solution reacts with copper (II) oxide, forming a blue solution.

Which two statements confirm the acidic nature of the solution?

A      1 and 2

B      1 and 3

C      2 and 4

D      3 and 4

3.    2 drops of methyl orange are added to 15 cm3 of dilute nitric acid in a conical flask. 10 cm3 of aqueous potassium hydroxide are then added gradually to the flask. Which changes occurs in the mixture in the conical flask?

A    Methyl orange changes colour from orange to red.

B    The concentration of the H+ ion decreases.

C    The pH value is lowered.

D    White precipitate is formed.

4.    X, Y and Z are elements in the same period of the Periodic Table. X forms an acidic oxide, Y forms a basic oxide and Z forms an amphoteric oxide. If X, Y and Z are placed in order of increasing atomic number, which order is correct?

A    X, Y, Z

B    X, Z, Y

C    Y, X, Z

D    Y, Z, X

5.    Which observation is true when an alkaline solution of potassium nitrate is warmed with aluminium powder?

A    Colourless and odourless gas is evolved. Gas relights glowing splinter.

B    Colourless and pungent gas is evolved. Gas turns moist red litmus paper blue.

C    Colourless and odourless gas is evolved. Lighted splinter extinguishes with ‘pop’ sound.
D    Colourless and pungent gas is evolved. Gas turns acidified potassium dichromate (VI) from orange to green.


1.    A

2.    D

3.    B

4.    D

5.    B