JAMB Chemistry Past Questions & Answers - Page 438

2,186.

Brass and bronze are both metallic alloys. Which of the following constituents is common to both alloys?

A.

Tin

B.

Zinc

C.

Copper

D.

Lead

E.

Aluminium

Correct answer is C

No explanation has been provided for this answer.

2,187.

If 30cm3 of oxygen diffuses through a porous pot in 7 seconds, how long will it take 60cm3 of chlorine to diffuse through the same pot, if the vapour densities of oxygen and chlorine are 16 and 36 respectively?

A.

9.3 sec

B.

14 sec

C.

21 sec

D.

28 sec

E.

30.3 sec

Correct answer is C

The rate of diffusion of a gas is proportional to the square root of the density.
16 and 7 secs
36 or 6 will be proportional to
7/16 x 6
7/4 x 6
But volume of chlorine is twice that of oxygen. The rate of escape of chlorine is
2/1 x 7/4 x 6/1 = 7 x 3; = 21 sec

2,188.

The IUPAC names of the compounds CH3COOH and CH2=CH2 are respectively;

A.

acetic acid and ethene

B.

methanoic acid and ethene

C.

methanoic acid and ethylene

D.

ethanol and ethene

E.

acetic acid and ethylene

Correct answer is A

The IUPAC id for \(CH_{3}COOH\) is Acetic acid, while for \(C_{2}H_{4}\) is ethene.

2,189.

The reaction between an organic acid and an alcohol in the presence of an acid catalyst is known as;

A.

saponification

B.

dehydration

C.

esterification

D.

hydrolysis

E.

hydration

Correct answer is C

Esterification, a reaction in which a carboxylic acid and an alcohol, heated in the presence of a mineral acid catalyst, form an ester and water:

2,190.

During the electrolysis of copper II sulphate between platinum electrodes, if litmus solution is added to the anode compartment,

A.

the litmus turns blue but no gas is evolved

B.

the litmus turns blue and oxygen is evolved

C.

the litmus turns blue and hydrogen is evolved

D.

the litmus turns red and oxygen is evolved

E.

the litmus turns red and then becomes colourless

Correct answer is D

Cu\(^+\) is  discharged preferentially at the cathode

OH\(^-\)  is  discharged preferentially at the anode

The presence of SO\(_4\)\(^2-\) and H\(^+\) makes the medium acidic

Which makes the litmus turns red and oxygen is evolved