JAMB Past Questions and Answers - Page 1244

6,216.

A gaseous metallic chloride MCl consists of 20.22% of M by mass. The formula of the chloride is?

[ M = 27, Cl = 35.5]

A.

MCl

B.

MCl\(_2\)

C.

MCl\(_3\)

D.

M\(_2\)Cl\(_6\)

Correct answer is C

  M Cl
% composition 20.22 79.78
Atomic mass 27 35.5
Mole ratio 20.22 79.78
  27 35.5
  0.75 2.25
Divided 0.75 0.75
  1 3

The formula of the Chloride = MCl\(_3\)

6,217.

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 

6,218.

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

6,219.

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.

6,220.

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