JAMB Chemistry Past Questions & Answers - Page 441

2,201.

A small quantity of solid ammonium chloride (NH4Cl) was heated gently in a test tube, the solid gradually disappears to produce two gases. Later, a white cloudy deposit was observed on the cooler part of the test tube. The ammonium chloride is said to have undergone?

A.

distillation

B.

sublimation

C.

precipitation

D.

evaporation

E.

decomposition

Correct answer is B

Sublimation is the transition of a substance directly from the solid phase to the gas phase without passing through the intermediate liquid phase 

2,202.

In the reaction between sodium hydroxide and sulphuric acid solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralise 10cm3 of 1.25 molar sulphuric acid?

A.

5cm3

B.

10cm3

C.

20cm3

D.

25cm3

E.

50cm3

Correct answer is E

\(2NaOH + H_{2}SO_{4} = Na_{2}SO_{4} + 2H_{2}O\)
V x 0.5M = 2(10 x 1.25)
0.5V = 2 x 12.5
0.5V = 25
V = \(\frac{25}{0.5}\) = \(50cm^{3}\)

2,203.

The periodic classification of elements is an arrangement of the elements in order of their

A.

Atomic Weights

B.

Isotopic Weights

C.

Molecular Weights

D.

Atomic Numbers

E.

Atomic Masses

Correct answer is D

Henry Moseley arranged the elements in the periodic table by their atomic number and this gave rise to the statement of the modern periodic law

2,204.

When sodium chloride and metallic sodium are each dissolved in water

A.

both processes are exothermic

B.

both processes are endothermic

C.

the dissolution of metallic sodium is endothermic

D.

the dissolution of metallic sodium is exothermic

E.

the dissolution of sodium chloride is explosive

Correct answer is D

When small quantities of sodium metal is added to water, there is an exothermic reaction, and they react to form sodium hydroxide and hydrogen.

2,205.

Zinc Oxide is a?

A.

Basic Oxide

B.

Acidic Oxide

C.

Amphoteric Oxide

D.

Neutral Oxide

E.

Reactive Oxide

Correct answer is C

Zinc oxide is an amphoteric oxide. 

- It will dissolve in both acids and alkalis