This question was attempted by most candidates and the performance was good.
In(a)(i), candidates correctly gave one example each of I – III from the list of examples thus:
I. FeCl3 /KOH/CaCl2/NaOH/MgCl2/P2O5.
II. CuO/CoCl2/conc H2SO4/ silica gel/CuSO4.
III. Na2CO3 IOH2O/ Na2SO4 IOH2O /MgSO4 7H2O .
IUPAC names of any of the compound was accepted instead of the formula.
In (a)(ii), candidates gave three products of the destructive of coal from the following:
- ammoniacal liquor
- coal tar
- coal gas
In(a)(iii), candidates correctly gave two uses of graphite from among the following uses:
- as lubricant
- as electrodes
- for making lead pencils
- moderators in nuclear reactors
In(b)(i), candidates correctly wrote a balanced chemical equation for the complete reaction thus:
H2SO4(aq) + 2NaOH(aq) → Na2SO4(aq) + 2H2O(l),
In(b)(ii), candidates correctly stated that the reaction is neutralization.
In(b)(iii), majority of the candidates could correctly calculate the number of moles of sodium hydroxide required for a complete reaction as follows:
No. of moles of H2SO4 = 20 x 0.125
= 0.0025 moles
1 mole of H2SO4 Ξ 2 moles of NaOH
∴ 0.005 moles of H2SO4 Ξ 2 x 0 . 0025 moles of NaOH
= 0.005 moles of NaOH.
Other correct method were accepted.
In (b)(iv), only few candidates could correctly outline how a solid sample of the product of the reaction in (b)(iii) could be obtained. The expected answer from candidates is as stated below:
- put solution into evaporating dish
- heat to concentrate/evaporate
- obtain the solid/allow to cool and crystallize.
In (c)(i), most candidates could not draw resonance structure of benzene. The correct structures expected from candidates are as follows:
In (c)(ii), only few candidates knew that benzene undergoes substitution and addition reactions.
In (c)(iii), most candidates gave chemical properties of benzene instead of physical properties: The expected answers were as follows:
- colourless liquid
- less dense than water
- insoluble in polar solvents/soluble in organic solvents
- has boiling point of 80ºC.