WAEC Past Questions and Answers - Page 1361

6,801.

The law of definite proportions states that

A.

pure samples of the same compound contain the same elements combined in the same proportion by mass

B.

pure samples of substances are in the same proportion by mass

C.

chemical compounds are pure because they contain the same elements

D.

matter can neither be created nor destroyed.

Correct answer is A

The Law of Definite Proportions states that all pure samples of a particular chemical compound contain similar elements combined in the same proportion by mass.

6,802.

Analysis of a hydrocarbon shows that it contains 0.93g of Carbon per gram of the compound. The mole ratio of carbon to hydrogen in the compound is [H = 1.0, C=12.0]

A.

1:1

B.

1:2

C.

2:1

D.

2:3

Correct answer is A

1g of Hydrocarbon = 0.93g of Carbon, therefore, Hydrogen = (1 - 0.93)g = 0.07g

    C       :      H

0.93       :      0.07

\(\frac{0.93}{12}\)   :   \(\frac{0.07}{1}\)

0.078         :        0.07

\(\frac{0.078}{0.07}    :    \frac{0.07}{0.07}\)

\(\approxeq   1:1\)

6,803.

Which of the following statements is true about ionic radius? Ionic radius

A.

increases as nuclear charge increases

B.

decreases as nuclear charge increases

C.

decreases as nuclear charge decreases

D.

remains constant as nuclear charge increases

Correct answer is B

No explanation has been provided for this answer.

6,804.

Which of the following methods can be used to seperate blood cells from plasma?

A.

Centrifugation

B.

Filtration

C.

Chromatography

D.

Distillation

Correct answer is A

No explanation has been provided for this answer.

6,805.

The change in the oxidation state of iron in the reaction represented by the equation:  \(2FeCl_{3} + H_{2}S \to 2FeCl_{2} + 2HCl + S\)  is

A.

+2 to +3

B.

0 to +2

C.

+3 to +2

D.

+3 to 0

Correct answer is C

The oxidation number of Iron in \(FeCl_{3}\) = +3. The oxidation number in \(FeCl_{2}\) = +2.