THE WEST AFRICAN EXAMINATIONS COUNCIL
West African Senior School Certificate Examination (WASSCE)
for School Candidates, 2023
CHEMISTRY 3 PRACTICAL
Instructions to Schools
1. Great care should be taken to ensure that the information given in items 2 and 3 below does not reach the candidates either directly or indirectly before the examination.
2. In addition to the fittings and reagents normally found in a Chemistry laboratory, the following apparatus and materials will be required by each candidate:
(a) one burette of 50 cm³ capacity:
(b) one pipette, either 20 cm³ or 25 cm³. All candidates at one centre
must use pipettes of the same volume. These should be clean and
free from grease;
(c) the usual apparatus for titration;
(d) the usual apparatus and reagents for qualitative work including the following with all reagents appropriately labelled:
i) dilute sodium hydroxide solution;
(ii) silver trioxonitrate (V) solution;
iii) aqueous barium chloride;
iv) dilute hydrochloric acid;
v) dilute trioxonitrate (V) acid;
(vi) aqueous ammonia;
(vii) acidified potassium dichromate solution;
(viii) dilute tetraoxosulphate (VI) acid;
(ix) lime water:
x) red and blue litmus papers.
f) filtration apparatus;
g) one beaker;
h) one boiling tube:
I) four test tubes;
j) methyl orange indicator;
l) wash bottle containing distilled/deionized water;
(m) burning splint:
(n) watch glass;
(o)Bunsen burner/source of heat:
(q) phenolphthalein indicator;
3. Each candidate should be supplied with the following. where ‘n
is the candidate’s serial number
(a) 150 cm³ of a solution of HCI in a corked fask or bottle labelled ‘En’. These: should all be the same containing 7.0 cm³ of concentrated HCI (about 36%) per dm of solution.
(b) 150 cm³ of NaOH solution in a corked flask or bottle labelled ‘Fn’.These should all be the same containing 3.2 g of NaOH per dm³ of solution.
c) One spatulaful of ammonium trioxocarbonate (IV) salt in a specimen bottle labelled Gn’. This must be the same for all candidates.
4. In all cases, more materials may be issued if required.
5. The actual concentrations of E and F must be stated on the Supervisor’s Report Form. The candidates will assume that the concentrations are exactly as stated in the question paper.
6. It should be noted that schools are not allowed to amend the information provided on the question paper or substitute any substance/solution for those specified in these instructions.
ARRANGEMENT AND SERIAL NUMBERS OF CANDIDATES
7. The laboratory places should be numbered serially and the candidates should be allotted these places strictly in the order of their index numbers. The number of every specimen supplicd to each candidate should be the same as his or her serial number.
8. If a candidate is absent, his or her serial number should not be allotted to another candidate.
9. If candidates are divided into a number of sets, the serial numbers should be continued through the sets, so that no serial number is repeated.
10. At the beginning of the examination, it should be ensured that the candidates record their serial numbers as well as their index numbers on the front page of their answer booklets, as they will be marked according to their serial numbers.
SUPERVISOR’S REPORT FORMS
11. Supervisor’s Report Forms are provioded separately. You must
enclose a completed Report Form in each envelope of scripts.
12. The chemistry teacher should carry out the titrations required of the candidates in question 1.
The titration figures should be up to at least one decimal place and should be carefully verified. Unless this is done at the the same time as the candidates own titrations, wide variatione could set in and the candidates may be unavoidably penalized.
13. Any particular difficulties experienced by any candidate should
be reported especially if the Examiner would be unable to discover these from the scripts.
CAUTION STATEMENT ON THE TOXICITY OF CHEMICALS
14. It is important to remind candidates that chemicals could be
dangerous when they are not handled properly.
Before the practical examination starts, read out the following
statements to candidates:
“Even though care has been taken to select the chemicals you will work with, you are being reminded that chemicals could be dangerous. It is therefore important that you handle them carefully.
Call the attention of your invigilator as soon as you start having any unusual sensation. Wash your mouth thoroughly with plenty of water, should any chemical get into it.
Remember to wash your hand thoroughly as soon as you finish
handling the chemicals.”
15. It is, however, expected that you will put the appropriate arrangement in place to prevent the occurrence of any accident.