WAEC 2024 CHEMISTRY PRACTICAL ANSWERS

VITAL INFORMATION

For question 1

Use your school’s endpoint and use it wherever you see our endpoint (18.13cm³) …and calculate with it

Replace our 18.13 in 1bi and do the calculation.

If your school wants to use mine, then the chemistry teacher must submit endpoint similar to ours without much difference…eg 18.13, 18.10, 17.90, 18.20, 18.30 etc

 

USE THIS NO.1….1b CORRECTED

(1a)
TABULATE PLEASE

Burette | Rough| 1st | 2nd

Final reading(cm³) | 19.00 | 18.10| 18.10|

Initial reading(cm³) | 0.00| 0.00| 0.00

Volume of A used(cm³) | 19.00| 18.10| 18.10|

Average titre = 18.10+18.10/2
= 18.10cm³

(1bi)
Conc. of B in mol/dm³ = ??
Ca = 0.020mol/dm³, Va = 18.10cm³
Na= 1, Nb = 5, Vb= 25.00cm³ , Cb= ??

CaVa/CbVb= Na/Nb

Cb = CaVaNa/VbNb

Cb= (0.020*18.10*5)/(25.0*1)
Cb= 0.0724mol/dm³

(1bii)
Con. of B in g/dm³ = ??
Con.(g/dm³) = Mass*1000/volume

= 3.8*1000/250
= 15.2g/dm³

(1biii)
FeSO₄<—> Fe²⁺ + SO₄²⁻
1 mol of FeSO₄ 1mol Fe²⁺
0.0724mol/dm³ xmol/dm Fe²⁺

x= 1*0.0724 = 0.0724mol/dm³

Mole= Con.*Vol/1000

Mole = 0.0724*250/1000
Mole= 0.0181mol

Mass= mole * m.m
= 0.0181*56
= 1.0136g

(1biv)
Percentage= 1.0136*100/15.2
= 6.67%

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(2)

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(3a
(i) Oxygen (O₂)
(ii) Carbon dioxide (CO₂)

(3b)
(i) Pipette
(ii) Burette

(3c)
A fume-cupboard is used to provide a safe enclosure for experiments that involve hazardous or toxic fumes, allowing for ventilation and protection of the experimenter and others in the lab.

(3d)
(i) Lab coats
(ii) Gloves
(iii) Goggles (or safety glasses)

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