JAMB Chemistry Past Questions & Answers - Page 37

181.

32g of anhydrous copper(ii)tetraoxosulphate(vi) dissolved in 1dm\(^3\) of water generated 13.0kj of heat. The heat solution is?

A.

26.0kj/mol

B.

65.0kj/mol

C.

130.0kj/mol

D.

260.0kj/mol

Correct answer is B

32g of CUSO\(_4\) liberate 13.0kj of heat

Molar mass of CUSO\(_4\) = 160g

No. of moles of CUSO\(_4\)  = 32g

No. of moles = 32(mass) / 160(molar mass)

= 0.2 moles

i.e 0.2 = 13kj

1 moles = xkj

: 65KJ 

182.

Helium is used in observation of ballons because it is?

A.

Light and combustible

B.

light and non-combustible

C.

heavy and combustible

D.

heavy and non-combustible

Correct answer is B

Helium floats because it is buoyant; its molecules are lighter than the nitrogen and oxygen molecules of our atmosphere and so they rise above it

183.

Chromatography is used to separate components of mixture which differ in their rates of ?

A.

diffusion

B.

migration

C.

reaction

D.

sedimentation

Correct answer is B

Chromatography is a method of separating mixtures by using a moving solvent on filter paper. The rate at which each solute moves up the paper depends on how strongly it is absorbed by the paper, and how soluble it is in the solvent.

184.

A few drop of conc HCL are added to about 10cm\(^3\) of a solution of PH 3.4. The PH of the resulting mixture is?

A.

less than 3.4

B.

greater than 3.4

C.

unaltered

D.

the same as that of the pure water

Correct answer is A

The addition of conc HCL makes the solution more acidic and the solution falls below the original value

185.

Which of the following gases will rekindle a brightly splint?

A.

NO\(_2\)

B.

NO

C.

N\(_2\)O

D.

CL\(_2\)

Correct answer is C

Nitrogen(I)Oxide rekindles a brightly glowing splinter but extinguishes a feebly glowing one which is not hot enough to decompose the gas to liberate oxygen