waecE-LEARNING
Chemistry Paper 2 (Essay) ,May/June 2011  
Questions:   1 2 3 4 5 6 7 8   Main
General Comments
Weakness/Remedies
Strength












































































Question 2

  • The following table gives the atomic numbers of elements V, W, X Y and Z.

    Element

    V

    W

    X

    Y

    Z

    Atomic number

    11

    16

    18

    19

    24

    (a        (i) Which of the elements belong(s) to group 1?
                 (ii) is/are noble gas(es)?
                 (iii)       form(s) coloured compound(s)?
              (iv)       form(s) an anion?
            (v)        react(s) with water to liberate hydrogen?
            (vi)       react(s) with water to form alkaline solution?

    (b)        What is the:
                (i)        charge on the ion formed in 2(a)(v) above?
                (ii)        group name of the element(s) 2(a)(i) above?

    (c)        (i)         Write the formula of the compound formed between element V and element W.
                (ii)        State the type of bond formed in 2(c)(i) above. Explain your answer.

    (d)       (i)         What is a covalent compound?
                (ii)        Give two factors that influence covalent bonding.
                (iii)       State the type of bond that exists in each of the following substances:
                            MgO, NH3 and Fe.
                (iv)       What are intermolecular forces?

  •  

    _____________________________________________________________________________________________________
    OBSERVATION

    Part (a), this was a popular question among the candidates. Most candidates identified the elements given in the question.
    In part (b), some candidates gave the group name wrongly as alkaline instead of alkali metals.  b(i) was well attempted by most candidates.
    In part (c), a few candidates mistook the type of bond as covalent bond and therefore give wrong explanation.
    In part (d), most candidates could not differentiate between the demands of covalent compound and covalent bond.  Almost all the candidates could not give the factors that affect covalent bonding.  Part d (iii) and (iv) were poorly attempted by most candidates.
    The expected responses were:
    (a)  (i)   and Y
          (ii)  X
          (iii) Z
          (iv) W
          (v)   V and Y
         (vi)   V and Y
         NOTE:  (Do not accept identified elements);

    (b)  (i)  -2/2-
          (ii)  alkali metals (Do not accept alkaline metals)

    (c)  (i)  V2 W (Do not accept identified elements)
         (ii)  Bond – ionic/electrovalent
                V can readily lose its electrons
                W can readily accept electrons to attain stability

    (d)  (i)   A compound formed by two atoms which donate equal number of electrons that
                 are shared between them such that each achieves a stable octet.
    (ii)-electronegativity (difference)                                                                                                           - ionization energy                                                                                                                            - electron affinity
    (iii)  MgO – ionic/electrovalent
            NH3 – covalent
             Fe – metallic
    (iv)  = Intermolecular forces are attractive forces that operate between molecules and influence the properties of the substance)

     

    Powered by Sidmach Technologies(Nigeria) Limited .
    Copyright © 2015 The West African Examinations Council. All rights reserved.