JAMB Past Questions and Answers - Page 1598

7,986.

5cm3 of a saturated solution of sodium chloride at 30°C gave, on careful evaporation, 1.95g of solid salt. The solubility of sodium chloride at 30°C?

(Na = 23, Cl = 35.5)

A.

5.00 mole dm3

B.

5.67 mole dm3

C.

6.00 mole dm3

D.

6.67 mole dm3

E.

7.00 mole dm3

Correct answer is D

1.95 gms of NaCl dissolves in 5 cm solution at 30°C
Number of gm of solute required to dissolve in
100 gm = (1.950 x 100)/ (5 x 1) = 1.95 x 20 = 39.0
390 gms will dissolve in 1000 dm3
Solution
Solubility of NaCl at 30°C in
(dm3 is 390)/(Mol wt g NaCl) = 6.67 mol dm3

7,987.

The electronic configuration of elements X and Y are X = 2, 8, 6; Y = 2, 8, 7. The bond in the compound formed by X and Y is expected to be?

A.

ionic

B.

covalent

C.

dative covalent

D.

metallic

E.

none of the above

Correct answer is B

No explanation has been provided for this answer.

7,988.

Which of the following is NOT a true statement of the kinetic Theory of Gases?

A.

The molecules move at random

B.

The size of molecules is negligble as compared with the volume of gas

C.

The molecular collisions are perfectly elastic

D.

Every molecule has the same kinetic energy at a particular temperature

E.

The average kinetic energy is proportional to the absolute temperature of the gas

Correct answer is D

No explanation has been provided for this answer.

7,989.

The products of the reaction between dilute sulphuric acid and sodium thiosulphate crystals are?

A.

Na2SO4 + SO2 + O2 + H2O

B.

Na2SO3 + SO3 + O2 + H2O

C.

Na2SO4 + SO2 + S + H2O

D.

Na2SO4 + SO3 + S + H2O

E.

Na2SO4 + SO2 + H2O only

Correct answer is C

\(Na_2S_2O_3 + H_2SO_4 → Na_2SO_4 + SO_2 + S↓ + H_2O\). Sodium thiosulfate reacts with sulfuric acid to produce sodium sulfate, sulphur dioxide, sulfur, and water.

7,990.

The following compounds are given with their corresponding boiling points.
Compound Boiling Point
i.................................14°C
ii................................24°C
iii................................0°C
iv................................120°C
V.................................-2°C
From the above information, indicate which of the following is correct?

A.

All the compounds are gaseous at 20 °C

B.

One of the compounds is gaseous at 20 °C

C.

Two of the compounds are gaseous at 20 °C

D.

Three of the compounds are gaseous at 20 °C

E.

None of the compounds is gaseous at 20 °C

Correct answer is D

No explanation has been provided for this answer.