Chemistry Paper 3,May/June 2014  
Questions:   1 2 3 Main
General Comments

Question 3

Consider the following experimental set-up.

(i)         Identify by name: P; Q; R; S and T.

            (ii)        State the method of collection of gas, S.

            (iii)       What is the function of R in the experimental set-up?

            (iv)       Write the balanced equation of the reaction for the
                        preparation of gas, S.
                                                                                                                                    [9 marks]




        This question is on theory of practical work.  Majority of the candidates
            that attempted this question did poorly.

            Some of the candidates lost marks because they used formulae in identifying
            the components instead of names.

            Also, some candidates used wrong lettering of symbols of elements in writing out the       equation.  e.g. instead of ‘Cl’ some candidates wrote ‘CL’ and ‘NACL’ instead of
            ‘NaCl’ etc.

            The expected answers include:

 (i)        P          -           Delivery tube                         
Q         -           Drying tower                          
R         -           Calcium oxide    (accept quicklime)
S          -           Ammonia gas                         
T         -           Retort stand with clamp        

(ii)        Upward delivery (of gas)/ downward displacement of air      

(iii)       To dry the gas

(iv)       Ca(OH)2(aq) + 2NH4Cl(aq) → CaCl2 + 2H2O + 2NH3(g)             



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