NECO GCE 2022 CHEMISTRY PRACTICAL ANSWERS;-EXAMGRAND.COM.NG

NECO GCE 2022 CHEMISTRY PRACTICAL ANSWERS

(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 = 0.11×22.5×1/1×25.0
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

(2ai)
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)
SO₂, H₂S Or CO₂ gas suspected

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

(2biii)
H₂s gas Evolved. S²- present

(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))

COMPLETED