NECO CHEMISTRY PRACTICAL ANSWERS 2022

(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= 0.1514.001/25.00*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)

Pink

(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.

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Teacher’s Report filling
1: A=0.15, B= 4.20
2 (i=14.00, ii=14.00, iii=14.00)

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TAKE NOTE

For question 1

Use your school’s endpoint and use it wherever you see our endpoint (13.20cm³) …and calculate with it.

Use the answer you got in 1b(i) to solve in 1b(ii) i.e we got 0.0396 in 1bi after calculating with our average titre (endpoint) value 0.0396, as u can see, we then used the 0.0396 in 1bii which we got from our calculation in 1bi.

NB: If you use our endpoint and your school teacher submits a different one with a wide margin to what u used, you will either fail or lose some mark in this particular question. Your school teacher should have in one way given you the average titre value(endpoint) or you might have gotten it in the lab from your past experiment.

If your school wants to use mine, then the chemistry teacher must submit endpoint similar to ours without much difference…eg 13.10, 13.20, 13.30, etc

COMPLETED!!!

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CHEMISTRY PRACTICAL SPECIMENS

INSTRUCTION(S) TO SCHOOL
In addition to the apparatus and reagents to be available in a secondary school chemistry laboratory, each candidate will require the following:

(a) One burette (50cm³)

(b) One pipette (20cm³/25cm³), however all candidates in a center must use pipettes of the same volume.

(c) The usual apparatus and reagents for qualitative work including;
(i) Dilute sodium hydroxide solution
(ii) Dilute ammonia solution
(iii) Dilute hydrochloric acid
(iv) Distilled water
(v) Red and blue litmus paper
(vi) Barium chloride solution
(vii) Phenolphthalein
(viii) Calcium hydroxide solution
(ix) Methyl orange
(x) One boiling tube
(xi) Five test tubes
(xii) Filtration apparatus
(xiii) source of heat

Each candidates should be supplied with the following, labelled An, Bn, Xn and Yn; where ‘n’ is the candidate’s serial number.

* 150cm³ of trioxonitrate(v) acid solution in a bottle labelled “An”. The acid solution which should be the same for all candidates will contain 9.50cm³ of concentrated trioxonitrate(v) acid per dm³ of solution.
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