2025 NECO CHEMISTRY: 2025 NECO CHEMISTRY PRACTICAL QUESTIONS AND ANSWERS (9966)

(1)
Tabulate
Titration; | rough | 1 | 2 | 3 |

Final; | 20.50 | 14.00 |14.00 | 14.00 |

Initial; | 0.00 | 0.00 | 0.00 | 0.00 |

Volume of A used; | 20.50 | 14.00 |14.00 | 14.00 |

Volume of pipette used
=25.00cm³

(1a)
Average volume of A used = 14.00+14.00+14.00/3
=14.00cm³ (Va)

2HNO³ + X²CO³ ---> 2XNO³ + H²O + CO²

(1bi)
Conc - of B in molldm³ = ?
Given;
Ca= 0.15molldm³
Vb= 25.00cm³
Va= 14.00cm³
Cb= ??
Na= 2
Nb= 1

Using;
CaVa/CbVb=Na/Nb
Cb= CaVaNb/VbNa
Cb= 0.15*14.00*1/25.00*2
Cb= 2.1/50
Cb= 0.042molldm³.

(1bii)
Molar mass of B =?
Using;
Conc(molldm³)= Conc(gldm³)/molar mass
0.042/1 * 4.20/m.m
m.m=4.20/0.042
m.m=100glmol

(1biii)
Value of x in x²(i)³=?
(2x)+12 + (16*3)= 100
2x+12+48=100
2x+60=100
2x=100-60=40
2x/2=40/2
x=20g/mol

(1ci)
(i)I ensure that the readings are taken at the lower meniscus
(ii)I ensure that my saliva did not enter the pipette while taking the base

(1cii)
Orange.

(2)
Tabulate

(2ai)
Under Observation;
An effervescence occurs in which a colorless and odourless gas which burns blue litmus red is evolved.

Under Inference;
CO² gas from CO3^²is suspected

(2aii)
Under Observation;
The gas turns lime water milky.

Under Inference;
CO² gas is confirmed.

(2b)
Under Observation;
Y dissolves completely in water

Under Inference;
Soluble salt

(2bi)
Under Observation;
White gelatinous PPT is formed.

Under Inference;
Al³+, Zn²+, Pb²+, present

(2bii)
Under Observation;
The white gelatinous PPT dissolve in excess NaOH

Under Inference;
Al³+, Zn²+, Pb²+, present

(2biii)
Under Observation;
White gelatinous PPT formed.

Under Inference;
Al³+, Zn²+, Pb²+, present

(2biv)
Under Observation;
The white gelatinous PPT remain insoluble in excess NH³

Under Inference;
Al³+, Pb²+, present.

(3ai)
It increases the boiling point of water

(3aii)
It requires heat to occur.

(3bi)
This is because it is deliquescent.

(3bii)
I. Calcium oxide
II. Anhydrous copper(ii) tetraoxosulphate(vi)

(3ci)
Hydrogen Chloride

(3cii)
I. To separate a mixture of immiscible liquids
II. To collect gases.