JAMB Chemistry Past Questions & Answers - Page 157

782.

Polystyrene is widely used as packaging materials for fragile objects during transportation because of its

A.

lightness

B.

low density

C.

high density

D.

high compressibility

Correct answer is D

EPS is known as one of the world’s most effective and lightweight insulation and packaging materials. It has low thermal conductivity and is moisture resistant, so it is often used as insulation against changing temperatures. Its high compressive strength gives it excellent shock absorption properties, making it an efficient packaging material.

783.

A hydrocarbon has an empirical formula CH and a vapour density of 39. Determine its molecular formula.

[C = 12, H = 1]

A.

C2H6

B.

C3H8

C.

C3H4

D.

C6H6

Correct answer is D

molecular mass = 2 x vapour density
= 2 x 39 = 79
∴ Cn Hn = 78
12n + 1n = 78
13n = 78
n = \(\frac{78}{13}\) = 6
∴ Cn Hn = C 6H 6

784.

CH3COOC2H5(1) + H2O(1) ⇌ CH 3COOH (aq) + C 2H 5OH (aq)

The purpose of H+ in the reaction above is to

A.

increase the yield of products

B.

maintain the solution at a constant PH

C.

increase the rate of the hydrolysis

D.

decrease the rate of the reverse reaction

Correct answer is C

The purpose of hydrogen ion is to speed up the decomposition of ethyl ethanoate to yield ethanoic acid and ethanol...so we can say that it is serving as a calalyst i.e increases the rate of hydrolysis.

785.

The polymer used in making car rear lights is

A.

perspex

B.

bakeelite

C.

polystyrene

D.

polyacrylonitrile

Correct answer is A

No explanation has been provided for this answer.