NECO GCE 2022 - CIVIC PRACTICAL CHEMISTRY ANSWER

(1ai)
Tabulate

Burette reading/cm3 | 1st titre | 2nd titre
Final reading/cm3 | 22.50 | 22.50
Initial reading/cm3 | 0.00 | 0.00
Volume of A used/cm3 | 22.50 | 22.50

(1aii)
This is used for the easy identification of end-point or neutrality point.

(1aiii)
To avoid error in measurement which may occur through droplet of A into the burette affecting the reading

(1bi)
Mass conc. of A = 4.015/dm3
Mass conc. of B = 5.55/dm3
Volume of A, Va = 22.5cm3
Volume of B, Vb = 25.0cm3
Molar mass of A, Hcl = 1+35.5
= 36.5g/mol

:- Conc. of A in mol/dm3 = ??
Conc. of A (mol/dm3) = conc. Of A (g/dm3) ÷ molar mass
= 4.015/36.5
Conc. of A = 0.11mol/dm3

(1bii)
Conc. of B in mol/dm3 = ??
Cb = ??
Ca = 0.11mol/dm3, Va = 22.5cm3, V6 = 25.0cm3, na = 1, nb = 1
CaVa/CbVb = na/nb
Cb = CaVanb/naVa
Cb = 0.11x22.5x1/1x25.0
Cb = 2.475/25.0
Cb = 0.099mol/dm3

(1biii)
Molar mass of B = ??
ing Conc (mol/dm3) = conc. (g/dm3) ÷ molar mass
Molar mass = conc. (g/dm3) ÷ conc. (mol/dm3)
Molar mass = 5.55/0.099
Molar mass = 56.0g/mol

(1biv)
XOH = 56
X + 16 + 1 = 56
X + 17 = 56
X = 56 - 17
X = 39

(1c)
Potassium

(1cii)
It is an analytical value

(1ciii)
KOH

(1civ)
Potassium hydroxide





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(2ai)
C is a soluble salt.

(2aii)
Ca²+ suspected.

(2aiii)
Ca2+ Present.

(2aiv)
Ppt remains insoluble.

(2av)
White Ppt formed which Remain insoluble

(2avi)
Brick red flame observed.

(2bi)
SOâ‚‚, Hâ‚‚S Or COâ‚‚ gas suspected

(2bii)
Lead(II) Ethanoate paper turns black

(2biii)
Gas is Hâ‚‚S .
S²- present

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(3ai)
I - KMnO4
II - Bromine water
III - Litmus paper

(3aii)
(i) A rotten egg odour is perceived
(ii) A colourless gas is formed
(iii) A green coloured compound is formed

(3bi)
I:
- A precipitate is formed
- Asoluble xompound is also formed

II:
- Filtration
- Decantation

(3bii)
AgNO3 (silver trioxonitrate(v))