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2018 WAEC Chemistry Theory (a) Arrange the three states of matter in order of decreasing: (i)        kinetic energy; (ii)       force of...

Chemistry
WAEC 2018

(a) Arrange the three states of matter in order of decreasing:
(i)        kinetic energy;
(ii)       force of cohesion.                                                         

 

(b) Consider the redox reaction equation:


(i)         State the change in oxidation number of:
I.          magnesium;
II.         hydrogen.

(ii)        Which of the species is being:
I.          oxidized;
II.         reduced?

(iii)       Identify the oxidizing agent.                                         

(c) (i) State two differences between boiling and evaporation.
(ii) What will be the effect of reduction of atmospheric pressure on the boiling point of water?                                                        

(d) For a given chemical equilibrium system, what is the significance of the equilibrium constant K?                                                    

(e) Consider the following organic compounds:
C\(_3\)H\(_7\)COOH; (CH\(_3\))\(_3\)COH.

Give the IUPAC name of each compound.                    

(f) Why are organic compounds classified on the basis of functional groups?                          
(g) State three differences between the solubility of solids in liquids and gases in liquids.                                                            

(h) Write a balanced chemical equation for the reaction between fluorine and water.        

(i) Define the term basicity of an acid.                               


     
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Explanation

(a)

(i)  gas > liquid > solid  / gas, liquid, solid

(ii)  solid > liquid > gas  / solid, liquid, gas                                                               


                                                                                                                       
(c) (i) 

(I)  0 to +2             
(II)  +1 to 0

             

(ii)(I)   Magnesium / Mg          
(II)   Hydrogen / H\(^+\) / HCl

 

(iii)  Hydrochloric acid / HCl
                                                                                                           
(d) (i)        

Evaporation

Boiling

-   occurs on the surface of  
Liquid

-  occurs at the entire length of
Liquid

-  occurs slowly

-  occurs rapidly

-  occurs at any temperature

-  occurs at specific temperature

-  produces cooling

-  does not produce cooling

-  occurs using internal energy/is   
Spontaneous

-  requires an external source of
Heat / not spontaneous

- bubbles are not seen

- bubbles are seen

                                                                       
(ii) The temperature required to boil the water decreases / boils at temperature lower than 1000 C    
                                                                                                                       
(e) The equilibrium constant k,  indicates the extent to which a reaction will proceed / it gives an idea of where the equilibrium lies / when k is large, more of the products are formed / when k is small, less of the products are formed.

(f)  C\(_3\)H\(_7\)COOH: butanoic acid                  
(CH\(_3\))3COH:   2 – methyl propan-2-ol   
                                                                                                           
(g) Functional groups are atoms or groups of atoms that are responsible for particular chemical properties and reactions of organic compounds.
                                                                                                           
(h)       

Solids in liquids

Gases in liquid

-  solubility increases with
temperature

-   solubility decreases as
temperature increases

- it is not affected by change in
pressure / does not have any
significant effect

-   is greatly affected by pressure,
increases with increase in pressure

-  increasing and decreasing of pH
affects the solubility

-  pH does not affect them

-  depends on the nature of solute
and solvent

-  depends on nature of gas and
solvent

                                   

(i)         2F\(_{2 (g)}\) + 2H\(_2\)O\(_{(l)}\) → 4HF\(_{ (aq)}\) + O\(_{2 (g)}\)

 

(j) is the number of replaceable hydrogen ions in a molecule of an acid / number of ionisable hydrogen atoms in one molecule of acid.


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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
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WAEC offline past questions - with all answers and explanations in one app - Download for free
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts