WAEC Past Questions and Answers - Page 1663

8,311.

Substances which absorb water from the atmosphere without dissolving in it are sid to be

A.

anhydrous

B.

hygroscopic

C.

insolube

D.

hydrated

E.

efflorescent

Correct answer is B

No explanation has been provided for this answer.

8,312.

How many electrons are removed from Cr2- when it is oxidized to CrO42-?

A.

0

B.

2

C.

4

D.

8

E.

10

Correct answer is D

From Cr2- to CrO42- involves 8 electrons to give oxidation state of Cr is +6

8,313.

What mass of copper would be deposited by a current of 1. 0 ampere passing for 965 seconds through copper (ll) tetraoxosulphate (IV) solution? [Cu = 63.5; 1F = 96500C]

A.

0.318g

B.

0.635g

C.

18g

D.

6.35g

E.

9.65g

Correct answer is A

Cu2+ + 2e- → Cu, From the equation 2 Faraday will liberate 63.5gm of copper The quantity of electricity passed (Q) Q = 1. 0 965 = 965 coulomb :. 2 x 96500 → 63.5, 965 → x. x = 965 / 2x96500 x 63.5 = 0.3175g \(\approx\) 0.328

8,315.

Which of the following will produce oxygen and hydrogen during its electrolysis using platinum electrode?

A.

Glucose solution

B.

Aqueous copper (ll) tetraoxosulphate (IV)

C.

Dilute sodium chloride solution

D.

Concentrated hydrochloric acid

E.

Dilute copper (ll) chloride solution

Correct answer is C

No explanation has been provided for this answer.