2017 - JAMB Chemistry Past Questions and Answers - page 4

In the preparation of sulphur dioxide by the action of dilute acids on sulphates and bisulphites. conc H₂SO₄ helps to release SO₂ from the mixture.

The setup represents the production of sulphur dioxide

M = (\frac{\text{Molar mass × Quantity of Electricity}}{\text{96500 × no of charge}})

= (\frac{MmIT}{96500n})

Copper II Chloride = CuCl₂

CuCl₂ → Cu²⁺ + 2Cl²

Mass of compound deposited = (\frac{\text{Molar mass × Quantity of Electricity}}{\text{96500 × no of charge}})

Q = IT

I = 0.5A

T = 45 × 60

T = 2700s

Q = 0.5 × 2700

= 1350c

Molarmass = 64gmol^-1

no of charge = + 2

Mass = (\frac{64 \times 1350}{96500 \times 2})

Mass = 0.448g

CH₂CH₂ - CCH₃CH₂

Start the numbering from the terminal carbon.

Iron [Fe] reacts with H₂ in the presence of oxygen to form a rust.

4Fe + 3O₂ → 2 Fe₂O₂

Fe₂O₃ + H₂O → Fe₂O₃.H₂O

The rate of dimension of a gas inversely proportional to the square root of its molecular mass or its density, which is Graham's Law of diffusion of gas.

R ∝ (\frac{1}{\sqrt{Mm}}) or R ∝ (\frac{1}{\sqrt{D}})

Dx = 0.5gdm^-3, Dy = 2gdm^-3

R= (\frac{K}{\sqrt{D}})

R(\sqrt{D}) = k

R₁(\sqrt{D_1}) = R₁(\sqrt{D_2})

R_x(\sqrt{D_x}) = R_y(\sqrt{D_y})

(\frac{R_x}{R_y}) = (\frac{\sqrt{D_y}}{\sqrt{D_x}})

= (\frac{\sqrt{2}}{\sqrt{0.5}})

= 2.0

Alkane's family are sp³ hybridized

Where −273°c = OK

i.e −273°c + 273 = OK

At zero kelvin, the volume of a gas becomes zero.

Molecular mass = vapour density X₂

Mm of XO₂ = x + 16(2) = x + 32

vapour density = 32

∴ x + 32 = 32 × 2

x + 32 = 64

x = 64 - 32

x = 32

∴ the relative molecular mass of X is 32

Relative molecular mass = vapour density × 2

Upward delivery works well for hydrogen and ammonia, which are both less densed than air. Sometimes, they are collected over water.

Bubbling of air through the acid solution removes deposited oxides of nitrogen.

Nitric acid is prepared in the laboratory by heating a nitrate salt with the concentrated acid.

NaNO₃ + H₂SO₄ → NaHSO₄ + HNO₃

Vapours of nitric acid are condensed to a brown liquid in a receiver cooled under cold water. "Dissolved oxides of nitrogen" e.g NO₂ are removed by redistillation or blowing a current of carbondioxide or dry air through the warm acid