JAMB Chemistry Past Questions & Answers - Page 388

1,936.

When a solid substance disappears completely as a gas on heating, the substance is said to have undergone

A.

evaporation

B.

distillation

C.

crystallization

D.

sublimation

Correct answer is D

No explanation has been provided for this answer.

1,937.

The principal constituent of natural gas is

A.

methane

B.

ethane

C.

propane

D.

butane

Correct answer is A

No explanation has been provided for this answer.

1,938.

Which of the following is found in cotton

A.

Starch

B.

Cellulose

C.

Fat

D.

Oil

Correct answer is B

No explanation has been provided for this answer.

1,939.

The process by which atoms are rearranged into different molecular structure in the petroleum refining process is referred to as

A.

catalytic cracking

B.

hydrocracking

C.

polymerization

D.

reforming

Correct answer is D

No explanation has been provided for this answer.

1,940.

A compound contains 40.0% carbon 6.7% hydrogen and 53.3% oxygen. If the molar mass of the compound is 180, find the molecular formula.
[H = 1, C = 12, O = 16]

A.

CH2O

B.

C3H6O3

C.

C6H12O6

D.

C6H12O3

Correct answer is C

C - 40% ; 40/12 = 3.33
H - 6.7% ; 6.7/1 = 6.7
O - 53.3% ; 53.3/16 = 3.33
C = 3.33/3.33 = 1
H = 6.7/3.33 = 2
O = 3.33/3.33 = 1
CH2O
(CH2O)n = 180
(12 + 2 + 16)~n = 180
30n = 180
n = 6
= C6H12O6