WAEC Past Questions and Answers - Page 1623

8,111.

Biotechnology is applied in the following except

A.

baking industry

B.

wine production

C.

production of antibiotics

D.

manufacture of soap

Correct answer is D

No explanation has been provided for this answer.

8,112.

If 20 cm3 of distilled water is added to 80 cm3 of 0.50 mol dm-3 hydrochloric acid, the concentration of the acid will change to

A.

20 mol dm-3

B.

0.40 mol dm-3

C.

2.00 mol dm-3

D.

5.00 mol dm -3

Correct answer is B

From M1V1 = M 2
V2; m 1 = 0.50 mol dm-3; m2 = ?; v1 = 80cm 3 = 100cm3
:. m2 = m1v2/v2 = 0.50 x 80/100 = 0.40 mol dm-3

8,113.

Which of the following on burning in air contributes to acid rain?

A.

Sulphur

B.

Magnesium

C.

Aluminium

D.

Zinc

Correct answer is A

No explanation has been provided for this answer.

8,114.

When sodium hydroxide solution is added to a solution of zinc salt, the white precipitate fromed redissolves in excess sodium hydroxide because

A.

sodium is more reactive than zinc

B.

sodium hydroxide is a strong alkali

C.

zinc hydroxide is amphoteric

D.

zinc hydroxide is unstable

Correct answer is C

No explanation has been provided for this answer.

8,115.

A colourless, odourless liquid T, gives effervesce with sodium trioxocarbonate (IV) and a white precipitate with silver trioxonitrate (V) solution T is most probably

A.

sodium chloride soluttion

B.

barium chloride solution

C.

dilute trioxonitrate (V) acid

D.

dilute hydrochloric acid

Correct answer is D

Take an unknown substance and add a few drops of it to the silver nitrate solution. If the silver nitrate solution turns white due to the formation of silver chloride, the acid is hydrochloric acid. If the solution remains clear, the acid is nitric acid. T is Hydrochloric Acid(an odorless,  colorless solution with a pungent smell)