WAEC Past Questions and Answers - Page 1355

6,771.

A 0.1\(moldm^{-3}\) solution of sodium hydroxide was diluted with distilled water to 0.001\(moldm^{-3}\). What is the dilution factor?

A.

1000.00

B.

100.00

C.

10.00

D.

0.01

Correct answer is D

Dilution factor = \(\frac{molar conc. of diluted}{molar conc. of undiluted}\)

= \(\frac{0.001}{0.1} = 0.01\)

6,772.

Which of the following statements about endothermic reaction is correct?

A.

Activation energy is high

B.

A catalyst is required

C.

It occurs reversibly

D.

Heat energy is absorbed

Correct answer is D

Endothermic reactions are those reactions which absorb energy from the surroundings and result in a net decrease in temperature.

6,773.

The use of diamond in abrasives is due to its

A.

high melting point

B.

hardness

C.

octahedral shape

D.

durability

Correct answer is B

Diamonds are very hard, they are often used as an abrasive.

6,774.

The properties of a good primary standard include the following except

A.

high molecular mass

B.

low molecular mass

C.

high degree of purity

D.

readily available

Correct answer is B

Characters of a good primary standard include: high purity, low reactivity with the air or surrounding environment, low hygroscopicity, large molar mass, a predictable reactivity and readily available.

6,775.

The bond angle in tetrahedral molecules such as tetrachloromethane is 

A.

180.0°

B.

109.5°

C.

105.5°

D.

90.0°

Correct answer is B

No explanation has been provided for this answer.