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Chemistry Paper 1 (Practical) ,May/June 2008  
Questions:       1 2 3 4 5 6   Main
General Comments

Question 6

(a) State one reagent and condition that could be used to identify proteins in the laboratory.    [2 marks]

(b) Calculate the mass of KOH required to prepare
             250 cm3 of  0.02 mol dm-3 solution.
                     [ K  =  39;  O  =  16;   H  =  1].  [3 marks]

(c)  State one use of a
(i)   separating funnel;
   (ii)   fumes chamber;
   (iii)   spatula. [3 marks]


This question was attempted by most candidates and the performance was good.

In (a), candidates correctly stated  addition of Million’s reagent/Biuret/(NaOH/CuSO4)/ conc. HNO3  and heat as the reagent and condition used to identify proteins in the laboratory.       

In (b), candidates correctly calculated the mass of KOH required to produce 250cm3 of 0.02 moldm-3  solution thus:  

(b)  Molar mass of KOH = 39 + 16 + 1 OR 56gmol-1
Mass  =  concentration x volume x molar mass

=   0.02 moldm-3  x  0.25 dm3   x   56 gmol-3  

=  0.28g
[other correct method was accepted]

In (c), candidates knew that separating funnel, fumes cupboard and spatula are used for separating two immiscible liquids, preparation of toxic/poisonous gases and scooping of solid/powdered reagents respectively

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