Oxidation and reduction - Jamb Chemistry Past Questions and Answers

Question 16:

• JAMB 1982

A current of 10.0A was passed for 1 hour through a solution of copper (ll) sulphate between the copper electrodes. Which of the following observation would be correct?
(1 Faraday = 96,500 coulobms) (i) 0.186 mole of copper is dissolved from the anode. (ii) 0.372 mole of copper is deposited on the cathode. (iii) the original Cu²⁺ ion concentration of the solution remains unchanged. (iv) the original Cu²⁺ ion concentration of the solution decreases.

A. I and ii
B. I and iii
C. I and iv
D. Ii and iii
E. Ii and iv

Question 17:

• JAMB 1982

In the preparation of carbon monoxide by heating ethanedioic acid with concentrated sulphuric acid, the concentrated sulphuric acid act as?

A. An oxidizing agent
B. A reducing agent
C. A dehydrating agent
D. A reaction medium
E. A catalyst

Question 18:

• JAMB 1983

In which of the following processes is iron being oxidized?
1 Fe + H₂SO₄ → FeSO₄ +H₂
2 FeSO₄ + H₂S → FeS + H₂SO₄
3 2FeCI₂ + Cl₂ → 2FeCl₃
4 2FeCl₃ + SnCl₂ + → 2FeCl₂ + SnCl₄

A. 1 only
B. 2 only
C. 3 only
D. 1 and 3
E. 2 and 4

Question 19:

• JAMB 1983

In the reaction Fe + Cu²⁺ \(\to\) Fe²⁺ + Cu,iron displaces copper ions to from copper. This is due to the fact that

A. Irn is in the metallic from while the copper is in the ionic from
B. The atomic weight of copper is greater than that of iron
C. Copper is greater than iron
D. Copper metal has more electrons than iron metal
E. Iron is higher in the electrochemical series than copper

Question 20:

• JAMB 1983

A gas that can behave as a reducing agent towards chlorine and as an oxidizing agent toward hydrogen sulphide is

A. O₂
B. NO
C. SO₂
D. NH₃
E. CO₂