WAEC Chemistry Past Questions & Answers - Page 61

301.

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

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

\(\approxeq   1:1\)

302.

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.

303.

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.

304.

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.

305.

The empirical formula of a compound containing 0.067mol Cu and 0.066mol O is    [Cu = 63.5, O = 16]

A.

\(Cu_{2}O\)

B.

\(CuO\)

C.

\(CuO_{2}\)

D.

\(CuO_{4}\)

Correct answer is B

    Cu   :   O

0.067   :   0.066

mole ratio   \(\frac{0.067}{0.066}\)  :  \(\frac{0.066}{0.066}\)

= 1   :   1

= CuO