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Neco 2023 Chemistry Practical Questions And Answers
By on July 13th, 2023. Neco



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

Average Volume of acid used = 21.50 + 21.50/2 = 21.50cm³

Solution B[Sodium trioxocarbonate (iv)] feels soapy

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

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

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

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


C + heat

Formation of yellow flame

Na⁺ present

C + distilled water + shake

It readily dissolve in water

C is a soluble in water

Solution C + litmus paper

It changes moist red litmus to blue and no effect blue

Solution C is alkaline

1st portion of solution C + barium chloride

White precipitate formed

CO₃²⁻ , SO₄²⁻ , S²⁻ or SO₃²⁻

Add dilute HCl to product in (bi)

White precipitate dissolved

CO₃ , SO₃²⁻ or S₃²⁻

To the second portion add phenolphthalein

Purple colour observed

C is alkaline

Sulphur (iv) oxide and hydrogen sulphide.

Liberation of hydrogen gas with pop sound and formation of green iron (ii) chloride solution

Spatula, beaker, weighing balance, standard volumetric flask

Solution turns red

Turns from brown to green

A colourless, odourless, acidic gas liberated which turns blue litmus paper red and turn lime water milky.

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