JAMB Chemistry Past Questions & Answers - Page 281

1,401.

Crude copper could be purified by the electrolysis of concentrated copper (II) chloride if the crude copper is?

A.

made both the anode and the cathode

B.

made the cathode

C.

made the anode

D.

dissolved in the solution

Correct answer is C

No explanation has been provided for this answer.

1,402.

What volume of oxygen measured at s.t.p would be liberated on electrolysis by 9650 coulombs of electricity?

(Molar volume of gas = 22.4 dm\(^3\), F = 96,500 C mol-)

A.

22.4 dm3

B.

11.2 dm3

C.

1.12 dm3

D.

0.560 dm3

Correct answer is D

For a diatomic divalent element like oxygen:

4 faraday (4 *  96,500) = 1 mole of the element  = Molar volume of gas = 22.4

: 4 *  96,500 = 22.4

  9650 = x 

: x = \(\frac{9650 * 22.4}{ 4 *  96,500}\)

x = 0.56dm\(^3\)

 

1,404.

Which of the following compounds is a base?

A.

CO2

B.

CaO

C.

H3PO3

D.

CH3COOCH3

Correct answer is B

No explanation has been provided for this answer.

1,405.

A few drops of concentrated HCI are added to about 10cm3 of a solution of pH 3.4. The pH of the resulting mixtures is?

A.

less than 3.4

B.

greater than 3.4

C.

unaltered

D.

the same as that of pure water

Correct answer is A

The addition of concentrated HCl to the solution makes the solution more acidic and the pH falls below the original value that is the pH value of the solution will now be less than 3.4.