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2001 WAEC Chemistry Theory (a) List two substances that can be used in the laboratory to (i) dry hydrogen;...

Chemistry
WAEC 2001

(a) List two substances that can be used in the laboratory to

(i) dry hydrogen;

(ii) remove carbon (IV) oxide from a sample of air;

(iii) convert hot copper (II) oxide to copper;

(iv) prepare zinc chloride by the action of dilute HCI.

 

(b)(i) Name two alloys which contain lead.

(ii) State and explain what is observed on bubbling H\(_2\)S into a solution of Pb(NO)\(_2\).

(iii) A metal M exists as a silvery white solid at temperatures above 18°C and as a grey solid below 18°C.

I. name the phenomenon exhibited by M.

II. What term is used to describe the temperature given as 18°C in this case?

 

(c)(i) Write an equation for the action of heat on each of the following compounds:

I. AgNO\(_3\)

II. (NH4)\(_2\)CO\(_3\).

 

(ii) Copy and complete the table below

Metal

Name of main ore Method of extraction

One major use Haematite

Haematite

Electrolysis of molten oxide


 

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Explanation

(a)(i) Fused calcium chloride and concentrated tetraoxosulphate (VI) acid.

(ii) Ca(OH)\(_2\), NaOH.

(iii) Hydrogen and carbon (II) oxide

(iv) Zn metals, zinc trioxocarbonate

(IV), zinc oxides.

 

(b)(i) Soft solder for welding and plumbing and type metal for printing.

(ii) a black precipitate of PbS\(_{(s)}\) is deposited

(iii)(i) Polymorphism

(ii) Transition temperature

 

(c)(i) 2AgNO\(_{3(s)}\) --> 2Ag\(_{(s)}\) + O\(_2\) + 2NO\(_{2}\).

                             Lustrous                Brown white

(ii) NH\(_4\)CO\(_3\) -> 2NH\(_3\) + CO\(_2\) + H\(_2\)O.

                          
(iii)

Metal

Name of main ore Method of extraction

One major use Iron

Iron Haematite Reaction process

Constfuction of vehicles

Aluminium

Bauxite Electrolysis of molten oxide

cables, paints, cooking utensils

 


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