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:
- orange/brick red precipitate
- no precipitate is formed/no visible reaction