WAEC Past Questions and Answers - Page 1656

8,276.

What volume of hydrogen is produced at s.t.p. When 2.60 g of zinc reacts with excess HCI according to the following equation? Zn(s) + 2HCI(aq) → ZnCI 2(aq) + H2(g) [Zn = 65; 1 mole of a gas occupies 22.4dm3 at s.t.p]

A.

0.040dm 3

B.

0.896dm 3

C.

5.82dm 3

D.

8.62dm 3

Correct answer is B

Zn + 2HCI → ZnCI2 + H2; 65g of Zn produces 22.4 dm3 of H2; .: 2.6g of Zn will produce = 2.6/65 x 22.4 = 0.896 dm3

8,277.

Gas molecules are said to be perfectly elastic because

A.

they collide without loss of energy

B.

they move about in straight lines

C.

the distances between them are negligible

D.

the volume occupied by them is negligible

Correct answer is A

No explanation has been provided for this answer.

8,278.

Equal volumes of CO2 cnd CO at s.t.p have the same

A.

mass

B.

density

C.

rate of diffusion

D.

number of molecules

Correct answer is D

No explanation has been provided for this answer.

8,279.

Which of the following movements can be described as random motion?

A.

wheelbarrow being pushed

B.

car travelling on a straight line

C.

Gas molecules colliding in a flask

D.

Planets going round the sun

Correct answer is C

No explanation has been provided for this answer.

8,280.

Exhaust fumes discharged from a smoky vehicle gradually become invisible as a result of

A.

diffusion

B.

combustion

C.

absorption

D.

emission

Correct answer is A

No explanation has been provided for this answer.