NECO June/July Exam Chemistry Practical questions And Answers Update 2024 Verified Solution

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The NECO Chemistry practical exam questions have been released. Access the verified NECO exam questions and answers for 2024, along with usage guidelines. The Chemistry exam is scheduled for tomorrow, July 3rd, 2024.

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2024 NECO June/July Exam Chemistry questions And Answers

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NECO Chemistry Practical questions Papers

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NECO Chemistry practical exam Answers

Solving/Typing……

(1)
Tabulate;
Burette readings;
|Rough |1st |2nd|3rd|

Final readings in cm³;
|22.00|20.10 |20.20|20.30|

Initial reading in cm³;
|0.00|0.00|0.00 |0.00|

Volume of A (acid) used cm³;
|22.00|20.10|20.20| 20.30|

The average titre
= 20.10+20.20+20.30/3
=60.60/3
= 20.20cm³

;Va 20.20cm³

(1bi)
Concentration of A in mol/dm³, Ca = ?

Concentration of A (g/dm³) = 4.40g/dm³.

.m.m of A, H²SO⁴ =(1*2)+(32*1)+(16*4)
=2+32+64
=98g/mol

Using concentration (mol/dm³) = Concentration (g/dm³)/m.m

Concentration (mol/dm³)
=4.40/98
=0.045mol/dm³

;: Concentration of A(mol/dm³) = 0.045mol/dm³

(1bii)
Concentration of B(mol/dm³) =???
Ca=0.045, Va=20.20, Vb=25.00, na=1, nb=1, cb=?

Using; CaVa/CbVb = na/nb
Cb=CaVanb/Vbna =0.045*20.20*1/25.00*1
Cb=0.036mol/dm³

(1biii)
Conc. of B(g/dm³) that reacted =??
molar mass of B, Na₂CO₃ = (23*2)+(12*1)+(16*3) = 106g/mol

Conc. of B(mol/dm³) = 0.036mol/dm3
Conc. (mol/dm³) = Conc. (g/dm³)/molar mass

(0.036/1) = Conc. (g/dm³)/106

Conc. (g/dm³) = 0.036*106 = 3.82g/dm³
Conc. of B(g/dm³) = 3.82/dm³

(1biv)
mass of the impurity in 1.0dm³ of B=??
Conc. of impurity (g/dm³) = 7.50 – 3.82 = 3.68g/dm³

:. Mass of impurity= Conc. (g/dm³) x vol. (dm³)
= 3.68×1 = 3.68g

(1bv)
Vol. of CO₂ produced in 1.0dm³ of B = ??

Mole of B= Conc. x Vol. (dm³)
Mole of B = 0.036*1
Mole of B =0.036mol

By proportion,
1mol of Na₂.10₃ = 1mol of CO₂

0.036mol of Na₂.10₃ = xmol of CO₂

mole of CO₂ produced = 1*0.036 = 0.036mol

:. Volume = mole * 22.4 = 0.81dm³

(2)
[FILL THE TABLE WITH THE INFORMATION BELOW]

(2ai)
-TEST: C+5 cm³ of distilled water and shake thoroughly. Divide the solution into two portions
-OBSERVATION: It dissolves completely to give a colourless solution
-INFERENCE: C is a soluble salt

(2aii)
-TEST: To the first portion, add NaOH solution in drops.
-OBSERVATION: A white gelatinous precipitate is formed
-INFERENCE: Al³⁺ and Zn²⁺ present

(2aiii)
-TEST: Then add NaOH in excess
-OBSERVATION: The precipitate dissolve to give a colourless solution
-INFERENCE: Zn²⁺ present

(2aiv)
-TEST: To the second portion, add NH₃ solution in drops
-OBSERVATION: A white precipitate is formed
-INFERENCE: Al³⁺ and Zn²⁺ present

(2av)
-TEST: then in excess
-OBSERVATION: The white precipitate dissolves in excess NH₃
-INFERENCE: Zn²⁺ is confirmed

(2bi)
-TEST: 2cm³ of solution D + soda lime, heat, test with litmus paper.
-OBSERVATION: Ammonia gas (NH₃) is evolved, turning red litmus paper blue.
-INFERENCE: Presence of NH₄⁺ ions.

(2bii)
-TEST: Solution D + NaOH solution + CuSO₄ solution
-OBSERVATION: A blue precipitate formed
-INFERENCE: Presence of peptide bonds (proteins or peptides).

 

(3ai)
I- to avoid the drop of the acid into the burette which will alter the reading
II- to avoid change in concentration and contamination
III- to avoid bubbles in the pipette

(3aii)
This can be done through crystallization. The solution is dissolved, heated to a high temperature and then allowed to cool. During cooling,the sodium chloride crystallized out.

(3bi)
(i)evaporating dish
(ii)Bunsen burner

(3bii)
Solubility

 

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2024 Chemistry Practical Specimens

Below are the National Examinations Council Chemistry specimens for the main exam.

Chemistry Laboratory, each candidate will require the following:
(a) One burette (50 cm³)
(b) One pipette (20 cm³ /25 cm³), however all candidates in a centre must
 use pipette of the same volume
3. (a) The usual apparatus and reagents for qualitative work including:
(i) Dilute sodium hydroxide solution
(ii) Dilute ammonia solution
(iii) Dilute hydrochloric acid
(iv) Barium chloride solution
(v) Distilled water
(vi) Red and blue litmus papers
(vii) Copper (II) tetraoxosulphate (VI) solution
(viii) 2.0 molar solution of HCI
(ix) Soda lime solution
(x) Methyl orange
(xi) One boiling tube
(xii) Five test tubes
(xiii) Filtration apparatus
(xiv) Source of heat

 

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