WAEC Past Questions and Answers - Page 1380

6,896.

Which of the following compounds is/are secondary alkanols?

i) CH3CH(CH3)CH3OH
ii) CH3CH2CH(OH)CH3
iii) CH3C(OH)(CH3)CH3

A.

I only

B.

II only

C.

I and III only

D.

II and III only

Correct answer is B

No explanation has been provided for this answer.

6,897.

Ripening of fruits is hastened by using

A.

Ethanol

B.

Ethane

C.

Ethene

D.

Ethyne

Correct answer is C

No explanation has been provided for this answer.

6,898.

When a compound X is heated with concentrated tetraoxosulphate(VI)acid, it produces an alkene. X ia an

A.

Alkane

B.

Alkanol

C.

Alkanoate

D.

Alkyne

Correct answer is B

No explanation has been provided for this answer.

6,899.

Amino acids are obtained from proteins by

A.

Hydrolysis

B.

Oxidation

C.

Polymerization

D.

Reduction

Correct answer is A

No explanation has been provided for this answer.

6,900.

Consider the following half-cell reactions.
Al(s) \(\to\) Al3+(aq) + 3e-
Cu2+(aq) + 2e- \(\to\) Cu(s)

The overall equation for the reaction is

A.

Al(s) + Cu2+(aq) \(\to\) Al3+(aq) + Cu(s)

B.

2Al(s) + Cu2+(aq) \(\to\) 2Al(aq) + Cu(s)

C.

2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)

D.

3Al(s) + 2Cu2+(aq) \(\to\) Cu(s) + 3Al3+(aq)

Correct answer is C

Al(s) \(\to\) Al3+(aq) + 3e- ______(i)
Cu2+(aq) + 2e- \(\to\) Cu(s) ________(ii)

To balance the electrons, multiply equation (i) by 2 and equation (ii) by 3 and then add the resulting equations

2Al(s) \(\to\)2Al3+(aq) + 3e-
3cu2+(aq) + 6e- \(\to\)3Cu(s)
2Al(s) + 3Cu2+(aq) \(\to\) 3Cu(s) + 2Al3+(aq)