1990 - JAMB Chemistry Past Questions and Answers - page 1

Which of the following is a physical change?

In a reaction: SnO + 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).

            2(12 g) carbon = 151 g SnO<sub>2</sub><br />

            24 g carbon =151 g SnO<sub>2</sub><br />

            = 0.302 kg SnO<sub>2</sub> = 24/151g χ 0.0302 kg carbon = 0.048 kg carbon<br />

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

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

Fe₂O_3(s) + 2Al_(s) → Al₂O₃ + 2Fe_(s) If the heats of formation of Al₂O₃ and Fe₂O₃ are - 1670 kj mol^-1 and - 822 kj mol^-1 respectively, the enthalpy change in kj for the reaction is ?

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

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

In the reaction:

2Hl_(g) ↔ H_2(g) + l_2(g)' ΔH = 10 kj;

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

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

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