NECO EXAM portal 2021/2022

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17/07/2023

AGRICULTURE PRACTICAL ANSWERS

(1a)

A - Watering Can.
B - Plier.
C - Knapsack Sprayer.

(1b)
Water Can are basic and suitable for small-scale hand-watering tasks, WHILE Knapsack Sprayer are more advanced and versatile tools used for both watering and spraying various liquids on crops and larger areas.

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17/07/2023

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14/07/2023

14/07/2023

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13/07/2023

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13/07/2023

NECO CHEMISTRY PRACTICAL SOLUTIONS
====================================
(1a)
[TABULATE]

Burette Reading (cm³) | Rough | Titration I | Titration II
Final Reading (cm³) | 21.50 | 43.00 | 22.00
Initial Reading (cm³) | 0.00 | 21.50 | 00.00
Volume of A used (cm³) | 21.50 | 21.50 | 22.00

(1ai)
Average Volume of acid used = 21.50 + 21.50/2 = 21.50cm³

(1aii)
Solution B[Sodium trioxocarbonate (iv)] feels soapy

(1bi)
Conc. B in mol/dm³ =?
Ca= 0.04, Va= 21.50cm³, na= 1
Cb= ? , Vb= 25.00cm³ nb= 1

CaVa/CbVb = na/nb = 0.04×21.50/Cb×25.00 = 1/1
Cb= 0.04×21.50/25.00 = 0.86/25.00
Cb= 0.0344mol/dm³

(1bii)
Conc. of B in g/dm³ = Conc. of B in mol/dm³ × molar mass of B

Molar mass of B(NaCO₃)= (23×2) + 12 + (16×3) = 106

:. Conc. of B in g/dm³ = 0.0344×106 = 3.6g/dm³

(1biii)
1 mole of Na₂Co₃ = 1mole of Na₂So₄

:. 0.0344 mole of Na₂Co₃ = 0.0344 mole of Na₂So₄
№ of mole= mass/ molar mass

Molar mass of Na₂So₄= (23×2)+32+(16×4)=142
:. 0.0344 = mass/142
Mass=142×0.0344=4.9g

(1biv)
1 mole of Na₂Co₃= 1 mole of CO₂

0.0344 mole of Na₂Co₃ = 0.0344 mole of CO₂
:. № of mole = volume/ molar volume = 0.0344 = volume of CO₂/22400cm³
=771cm³
========================================

(2ai)
[TABULATE]

=TEST=
C + heat

=OBSERVATION=
Formation of yellow flame

=INFERENCE=
Na⁺ present

(2aii)
=TEST=
C + distilled water + shake

=OBSERVATION=
It readily dissolve in water

=INFERENCE=
C is a soluble in water

(2aiii)
=TEST=
Solution C + litmus paper

=OBSERVATION=
It changes moist red litmus to blue and no effect blue

=INFERENCE=
Solution C is alkaline

(2bi)
=TEST=
1st portion of solution C + barium chloride

=OBSERVATION=
White precipitate formed

=INFERENCE=
CO₃²⁻ , SO₄²⁻ , S²⁻ or SO₃²⁻

(2bii)
=TEST=
Add dilute HCl to product in (bi)

=OBSERVATION=
White precipitate dissolved

=INFERENCE=
CO₃ , SO₃²⁻ or S₃²⁻

(2biii)
=TEST=
To the second portion add phenolphthalein

=OBSERVATION=
Purple colour observed

=INFERENCE=
C is alkaline
========================================

(3ai)
Sulph

13/07/2023

NECO-CHEMISTRY-PRACTICALS-ANSWERS

(1a)
[TABULATE]

Burette Reading (cm³) | Rough | Titration I | Titration II
Final Reading (cm³) | 21.50 | 43.00 | 22.00
Initial Reading (cm³) | 0.00 | 21.50 | 00.00
Volume of A used (cm³) | 21.50 | 21.50 | 22.00

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