Social Science
Literature Arabic Islamic Studies C.R.K HistoryMusicVisual Art Clothing/Textile Home Management Shorthand
Chemistry Paper 2,Nov/Dec 2009  
Questions:   1 2 3 4 5 6 7 8   Main
General Comments

Question 2

  1. Consider the following reaction scheme

            (i)         Name:
                        I.          substances Q and R;
                        II.        reagent P;

  1. reaction Y;
  2. catalyst X.

           (ii)         Write an equation to illustrate reaction Y.                              [6 marks]

(b)        What is meant by a functioning group?                                              [2 marks]

(c)        A polymer is represented by the following formula:
            (i)         State the functional groups present in the polymer.
(ii)        Which of the functional groups in 2(c(i) can

  1. be oxidized,
  2. undergo hydrolysis?

[5 marks]

(d)       (i)         Draw the structures of three isomers of C3H6CƖ2 and name them.
            (ii)        Name the type of reaction that produces C3H6CƖ2 from C3H8  and CƖ2.
            (iii)       How many moles CƖ2 produced 1 mole of C3H6CƖ2?
                                                                                                                        [10 marks]

(e)        State what happens when Fehling’s solution is added to each of the following solutions and then heated:
            I.          glucose solution;

            II.        sucrose solution.                                                                      [2 marks



The question was attempted by most candidates and the performance was fair.

In part (a)(i) I-IV, candidates named substances Q and R, reagent P, reactant Y and catalyst X respectively.  However, some of them lost marks because they wrote the formulae instead of the names.
The expected answers from candidates were:

            I           Q = yeast, R = water
            II         reagent P = concentrated tetraoxosulphate VI
            III        Y= oxidation
            IV        X = (concentrated) tetraoxosulphate(VI) acid.

In (a)(ii), candidates correctly wrote an equation to illustrate Y as follows;
C2H5OH(Ɩ)       [oxidation]      CH 3COOH(Ɩ)
In part (b), candidates correctly defined functional group as an atom/group of atoms responsible for the characteristic chemical reactions of a compound.

In part (c)(i), candidates correctly stated the functional groups present in the polymer. However, many of them could not state the alkyl alkanoate group hence lost the mark,  The expected response from candidates were as follows:

            -           carboxy/alkanoic group (-COOH)
-           alkylalkanoate group ( -COO(CH2)m )
-           hydroxyl group ( - OH ).

In (c) (ii), candidates correctly stated that  -OH would be oxidized and –COOH would be hydrolysed in I and II respectively.

In part (d)(i), only very few candidates could correctly draw the structures of the three isomers of C3H6CƖ2 and give their names.

The expected structures and name of the isomers were as shown below:

(i)                         Cl     H     H                         H    H    H
                             |       |       |                            |       |      |     
          H - C  - C  -  C  - H             H -  C – C – C - H
                                         |       |       |                            |       |       |
                                        Cl    H     H                         Cl    Cl     H                  
                 1,1 – dichloropropane                        1,2  - dichloropropane                                

                           H     Cl     H                        Cl     H    Cl 
                             |       |       |                            |       |       |     
          H - C  - C  -  C  - H             H -  C – C – C - H
                                         |       |       |                            |       |       |
                                        H    Cl     H                         H     H     H                  
     2,2 – dichloropropane                         1,3  - dichloropropane   


In (d) (ii), candidates correctly stated the type of reactions as chlorination/substitution and 2 moles of chlorine molecule / 1 mole of chlorine molecule in (iii).

In (e), candidates correctly stated what happened when Fehling’s solution was added to glucose solution and sucrose solution respectively.  However, some of them lost the marks because of lack of knowledge of test on food substances.

The expected responses from candidates were:  

  1. orange/brick red precipitate
  2. no precipitate is formed/no visible reaction
Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2012 The West African Examinations Council. All rights reserved.