WAEC Chemistry Past Questions & Answers - Page 188

936.

What volume of 0.20 mol dm -3 NaOH solution would yield 5.0 g of NaOH on evaporation to dryness? [NaOH = 40g mol-1]

A.

400 cm3

B.

625 cm3

C.

1000 cm3

D.

1600 cm 3

Correct answer is B

Conc. g/dm3 = 0.20 x 40 gmol -1 = 8 g/dm3
1000 cm3 of 0.20m NaOH contains 8g of NaOH :. 5g of NaOH will be contained in 5/8 x 1000 x 625cm3

937.

When excess ethene is shaken with acidified KMnO4 solution, the product obtained is

A.

ethane

B.

ethanal

C.

ethane - 1, 2 - diol

D.

ethanoic acid

Correct answer is C

No explanation has been provided for this answer.

938.

What process does the following equation represent ? n(C\(_{6}\)H\(_{10}\)O\(_{5}\)) + nH\(_{2}\)O → nC\(_{6}\)H\(_{12}\)O\(_{6}\) ?

A.

Polymerization of glucose

B.

Hydrolysis of starch

C.

Fermentation of sugar

D.

Dehydration of carbohydates

Correct answer is B

The enzyme amylase is secreted out of the cells (an exoenzyme) into the surrounding media, catalyzing the breakdown of starch into smaller sugars which can then be absorbed by the cells for use.

939.

The reaction of vegetable oil with a solution of wood ash is

A.

saponification

B.

neutralization

C.

hydrogenation

D.

esterification

Correct answer is A

No explanation has been provided for this answer.

940.

What is the organic product of the reaction of C2H 5OH with excess acidified K 2Cr 2O7(aq)?

A.

CH3COOH

B.

C2H5OC2H5

C.

HCOOCH 3

D.

C2H5CHO

Correct answer is A

No explanation has been provided for this answer.