JAMB Past Questions and Answers - Page 1542

7,706.

The empirical formula of an oxide of nitrogen containing 30.4 per cent of nitrogen is (N=14.0,O=16.0)

A.

N2O2

B.

NO

C.

NO2

D.

N2O

E.

N2O3

Correct answer is C

No explanation has been provided for this answer.

7,707.

In the electrolysis of dilute sulphuric acid using platinum electrodes, the products obtained at the anode and cathode are:
Anode Cathode

A.

Sulphur hydrogen

B.

Hydrogen oxygen

C.

Oxygen Hydrogen

D.

Hydrogen sulphate ions

E.

Sulphur oxygen

Correct answer is C

Dissociation of sulfuric acid,

\(H_2SO_4→2H^+_{(aq)}+SO^{−2}_{4(aq)}\)

Dissociation of water,

\(H_2O→H^+_{(aq)} + OH^−_{(aq)}\)

At Anode : \(4OH^−→2H_2O_{(l)} + O_{2(g)} + 4e_{−}\)

At Cathode : \(2H^+_{(aq)}  + 2e^− → H_{2(g)}\)

7,708.

12 g of solid protassium chlorate (KCIO) were added to 40 g of water and heated to dissolve all the solid. As the solution cools, crystals of potassium chlorate at 66 oC. The solubility of potassium chlorate at 66 oC is therefore?

A.

66

B.

33

C.

10

D.

20

E.

30

Correct answer is E

solubility = \(\frac{solute x 100}{solvent}\)

The solubility of KClO3 at 66oC will be \(\frac{12}{40} \times \frac{100}{1}\)

= 30

7,709.

If chlorine gas is bubbled into water and then this yellowish-green coloured solution is exposed to bright sunlight for a while

A.

the solution will give out chlorine gas and hydrogen chloried gas

B.

the solution will produce chlorine gas and oxygen

C.

the solution will give out solution will producing hypochloric acid

D.

the solution is decomposed giving out oxygen, hydrogen and chlorine

E.

the solution will give out oxygen gas leaving behind aqueous hydrochloric acid

Correct answer is E

No explanation has been provided for this answer.

7,710.

When ammonium, potassium and calcium carbonates are each separately heated

A.

none of them will decompose

B.

each of them will decompose to give carbondioxide and the respective oxide

C.

ammonium carbonate and potassium carbonate will not decompose

D.

only ammonium carbonate and the respective oxide

E.

ammonium carbonate will decompose to give carbondioxide, water and ammonia

Correct answer is E

Solid ammonium carbonate decomposes as it is heated.

 (NH4)2CO3 → 2 NH3 + CO2 + H2O