Metals and their compounds - Jamb Chemistry Past Questions and Answers

Question 21:

• JAMB 1981

For iron to rust, there should be present?

A. Oxygen
B. Moisture
C. Carbondioxide
D. Oxygen and moisture
E. Oxygen, moisture and carbondioxide

Question 22:

• JAMB 1981

Allotropes are elements having?

A. Different physical but the same chemical properties
B. Different chemical but the same physical properties
C. The same chemical and physical properties
D. Different atomic structure
E. The same position in the periodic table

Question 23:

• JAMB 1981

Which of the following statements about phosphorus is NOT correct?

A. Phosphorus is a solid mineral
B. Phosphorus is obtained by oxidation reaction of phosphate
C. Phosphorus exists in two allotropic forms
D. Both forms of phosphorus are interconvertible
E. Yellow phosporus ignites when rubbed on a rough surface

Question 24:

• JAMB 1981

In the extraction of iron, which of the following reactions does NOT take place in the blast furnace?

A. CO₂ + C → 2CO
B. 2Fe₂O₃ + 3C → 4Fe + 3CO₂
C. Fe₂O₃ + 3C → 2Fe + 3CO₂
D. CaCO₃ → CaO + CO₂
E. CaO + SiO₂ → CaSiO₃

Question 25:

• JAMB 1981

4g each of aluminium foil and aluminium powder were introduced respectively into flasks P and Q.
Flask P was treated with warm bench sodium hydroxide and all the aluminium dissolved in one hour. Flask Q was treated with cold sodium hydroxide and all the aluminium dissolved in 10 minutes. What was responsible for Q reacting faster than P?

A. There were more aluminium atoms in Q than P
B. The heat given off in retarded the reaction
C. Q generated more pressure than P during the reaction
D. P generated more pressure than Q
E. Q has a greater surface area for the reaction than P