Year : 
1990
Title : 
Chemistry
Exam : 
JAMB Exam

Paper 1 | Objectives

1 - 10 of 49 Questions

# Question Ans
1.

Which of the following is a physical change?

A. The bubbling of chlorine into water

B. The bubbling of chlorine into a jar contanining hydrogen

C. The dissolution of sodium chloride in water

D. The passing of steam over heated iron

C
2.

In a reaction: \(SnO_{2} + 2C → Sn + 2CO\) the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).

A. 0.40 kg

B. 0.20 kg

C. 0.06 kg

D. 0.04 kg

Detailed Solution

In the reaction: \(SnO_{2} + 2CO\)
From the equation above
2(12 g) carbon = 151 g \(SnO_{2}\)
24 g carbon =151 g \(SnO_{2}\)
= 0.302 kg \(SnO_{2}\) = 24/151g χ 0.0302 kg carbon = 0.048 kg carbon

Mass of coke is required not mass of carbon,so it is (0.048\(\times\)100)\(\div\)80 = 0.06
3.

Cr2O7 + 6Fe2+ + 14H+ → 2Cr3+ +6Fe3+ + 7H2O. In the above , the oxidation number of chromium changed from?

A. +7 to +3

B. +6 to +3

C. +5 to +3

D. -2 to +3

A
4.

In the reaction 1O-3 + 5l- + 6H+ → 312 + 3H2O, the oxidizing agent is?

A. H+

B. l-

C. 1O-

D. l2

C
5.

Fe\(_2\)O\(_{3(s)}\) + 2Al\(_{(s)}\) → Al\(_2\)O\(_3\) + 2Fe\(_{(s)}\). If the heats of formation of Al\(_2\)O\(_3\) and Fe\(_2\)O\(_3\) are - 1670 kJmol\(^{-1}\) and - 822 kJmol\(^{-1}\) respectively, the enthalpy change in kJ for the reaction is ?

A. +2492

B. +848

C. -848

D. -2492

Detailed Solution

Heat of formation = Heat of products - Heat of reactants
= - 1670 - (- 822)
= - 1670 + 822
= - 848 kJ
6.

Iron galvanized with zinc is cathodically protected from corrosion. This is because?

A. zinc has a more positive oxidation potential than iron

B. zinc has less positive oxidation potential than iron

C. bith have the same oxidation potential

D. zinc is harder than iron

B
7.

Which of the following samples will react fastest with dilute trioxonitrate (V) acid?

A. 5 g of lumps of CacO3 at 25°C

B. 5 g of powered CacO3 at 25°

C. 5 g of lumps of CaCO3 at 50°C

D. 5 g of powered CaCO3 AT 50°C

D
8.

In the reaction:
2Hl(g) ↔ H2(g) + l2(g)' ΔH = 10 kj;

The concentration of iodine in the equilibrium mixture can be increased by?

A. raising the pressure

B. raising the temperature

C. adding a catalyst

D. lowering the pressure

B
9.

Which of the following gases can be collected by the upward displacement of air?

A. NO

B. H 2

C. NH3

D. Cl 2

D
10.

The brown fumes given off when trioxonitrate (V) acid is heated consist of ?

A. NO2 and O2

B. H2O and NO2

C. NO2' O2 and H2O

D. NO, NO2 and H2O

C
1.

Which of the following is a physical change?

A. The bubbling of chlorine into water

B. The bubbling of chlorine into a jar contanining hydrogen

C. The dissolution of sodium chloride in water

D. The passing of steam over heated iron

C
2.

In a reaction: \(SnO_{2} + 2C → Sn + 2CO\) the mass of coke containing 80% carbon required to reduce 0.302 kg of pure tin oxide is?
(Sn - 119, O - 16, C - 12).

A. 0.40 kg

B. 0.20 kg

C. 0.06 kg

D. 0.04 kg

Detailed Solution

In the reaction: \(SnO_{2} + 2CO\)
From the equation above
2(12 g) carbon = 151 g \(SnO_{2}\)
24 g carbon =151 g \(SnO_{2}\)
= 0.302 kg \(SnO_{2}\) = 24/151g χ 0.0302 kg carbon = 0.048 kg carbon

Mass of coke is required not mass of carbon,so it is (0.048\(\times\)100)\(\div\)80 = 0.06
3.

Cr2O7 + 6Fe2+ + 14H+ → 2Cr3+ +6Fe3+ + 7H2O. In the above , the oxidation number of chromium changed from?

A. +7 to +3

B. +6 to +3

C. +5 to +3

D. -2 to +3

A
4.

In the reaction 1O-3 + 5l- + 6H+ → 312 + 3H2O, the oxidizing agent is?

A. H+

B. l-

C. 1O-

D. l2

C
5.

Fe\(_2\)O\(_{3(s)}\) + 2Al\(_{(s)}\) → Al\(_2\)O\(_3\) + 2Fe\(_{(s)}\). If the heats of formation of Al\(_2\)O\(_3\) and Fe\(_2\)O\(_3\) are - 1670 kJmol\(^{-1}\) and - 822 kJmol\(^{-1}\) respectively, the enthalpy change in kJ for the reaction is ?

A. +2492

B. +848

C. -848

D. -2492

Detailed Solution

Heat of formation = Heat of products - Heat of reactants
= - 1670 - (- 822)
= - 1670 + 822
= - 848 kJ
6.

Iron galvanized with zinc is cathodically protected from corrosion. This is because?

A. zinc has a more positive oxidation potential than iron

B. zinc has less positive oxidation potential than iron

C. bith have the same oxidation potential

D. zinc is harder than iron

B
7.

Which of the following samples will react fastest with dilute trioxonitrate (V) acid?

A. 5 g of lumps of CacO3 at 25°C

B. 5 g of powered CacO3 at 25°

C. 5 g of lumps of CaCO3 at 50°C

D. 5 g of powered CaCO3 AT 50°C

D
8.

In the reaction:
2Hl(g) ↔ H2(g) + l2(g)' ΔH = 10 kj;

The concentration of iodine in the equilibrium mixture can be increased by?

A. raising the pressure

B. raising the temperature

C. adding a catalyst

D. lowering the pressure

B
9.

Which of the following gases can be collected by the upward displacement of air?

A. NO

B. H 2

C. NH3

D. Cl 2

D
10.

The brown fumes given off when trioxonitrate (V) acid is heated consist of ?

A. NO2 and O2

B. H2O and NO2

C. NO2' O2 and H2O

D. NO, NO2 and H2O

C