WAEC Chemistry Past Questions & Answers - Page 88

436.

An unsaturated solution differs from a saturated solution at a given temperature because it

A.

Cannot dissolve more solute

B.

Can hold more solute than it can actually dissolve

C.

Can still dissolve more solute at given temperature

D.

Form crystal more easily on cooling

Correct answer is C

An unsaturated solution contains a lesser amount of solute than that in a saturated solution. It can go on to dissolve more quantities of solute at the same temperature until it becomes a saturated solution.

437.

Aluminium is used in the manufacture or aircraft because it

A.

Is hard and brittle

B.

Is light and resists corrosion

C.

Has high density and conducts electricity

D.

Is malleable and ductile

Correct answer is B

No explanation has been provided for this answer.

438.

Metals can be stretched into wires because they are

A.

Ductile

B.

Good conductors

C.

Lustrous

D.

Malleable

Correct answer is A

No explanation has been provided for this answer.

439.

The mass of potassium hydroxide required to make 300.ocm3 of 0.4 moldm-3 solution is {KOH = 56.0}

A.

26.88g

B.

13.44g

C.

6.72g

D.

3.36g

Correct answer is C

300cm3 of 0.4moldm3

1000cm3 contains 0.4mole

300cm3 will contain \(\frac{300 \times 0.4}{1000}\)

= 0.12mole

Number of moles = \(\frac{Mass}{\text {Molecular mass}}\)

Mass = number of moles x m.mass

= 0.12 x 56 = 6.72g

440.

Chemicals that are produced in small quantities and with very degree of purity are

A.

Bulk chemicals

B.

Fine chemicals

C.

Heavy chemicals

D.

Light chemicals

Correct answer is B

No explanation has been provided for this answer.