Year : 
2018
Title : 
Chemistry
Exam : 
WASSCE/WAEC MAY/JUNE

Paper 1 | Objectives

31 - 40 of 50 Questions

# Question Ans
31.

When chlorine is passed through a sample of water, the pH of the water sample would be

A. < 7

B. > 7

C. = 7

Detailed Solution

\(Cl_{2} + H_{2}O \to HCl + HOCl\)
The two compounds in the product end are acidic and hence, their mixture is acidic. Hence, the pH is < 7
32.

How many atoms are contained in 0.2moles of nitrogen? \([N_{A} = 6.02 \times 10^{23}]\)

A. \(1.20 \times 10^{23}\)

B. \(2.41 \times 10^{23}\)

C. \(3.62 \times 10^{23}\)

D. \(4.82 \times 10^{23}\)

Detailed Solution

\(1 mole = 6.02 \times 10^{23} atoms\)
\(0.2 moles = 6.02 \times 10^{23} \times 0.2\) atoms
= \(1.204 \times 10^{23}\)
\(\approxeq 1.2 \times 10^{23}\)
33.

The strength of metallic bonds depends on the

A. charge density of the atoms

B. ductility of the metal

C. number of valence electrons

D. total number of electrons in the atom

Detailed Solution

It is determined by the difference in the electron structures of the atoms. These primarily are: The number of outer electrons, i.e the number of valence shell electrons released during a metallic bond.
34.

When zinc is added to AgNO\(_{3}\) solution, crystals of silver forms on the zinc surface. This indicates that zinc is

A. oxidised

B. reduced

C. decomposed

D. dissociated

Detailed Solution

Reaction: \(2AgNO_{3} + Zn \to Zn(NO_{3})_{2} + 2Ag\)
The oxidation number of Zn in the reactant is 0, and in the product is +2. Therefor, it is oxidized.
35.

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. \(CuO_{4}\)

Detailed Solution

Cu : O
0.067 : 0.066
mole ratio \(\frac{0.067}{0.066}\) : \(\frac{0.066}{0.066}\)
= 1 : 1
= CuO
36.

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

Detailed Solution

The oxidation number of Iron in \(FeCl_{3}\) = +3. The oxidation number in \(FeCl_{2}\) = +2.
37.

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

A. Centrifugation

B. Filtration

C. Chromatography

D. Distillation

A
38.

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

B
39.

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

Detailed Solution

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
\(\frac{0.078}{0.07} : \frac{0.07}{0.07}\)
\(\approxeq 1:1\)
40.

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.

Detailed Solution

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.
31.

When chlorine is passed through a sample of water, the pH of the water sample would be

A. < 7

B. > 7

C. = 7

Detailed Solution

\(Cl_{2} + H_{2}O \to HCl + HOCl\)
The two compounds in the product end are acidic and hence, their mixture is acidic. Hence, the pH is < 7
32.

How many atoms are contained in 0.2moles of nitrogen? \([N_{A} = 6.02 \times 10^{23}]\)

A. \(1.20 \times 10^{23}\)

B. \(2.41 \times 10^{23}\)

C. \(3.62 \times 10^{23}\)

D. \(4.82 \times 10^{23}\)

Detailed Solution

\(1 mole = 6.02 \times 10^{23} atoms\)
\(0.2 moles = 6.02 \times 10^{23} \times 0.2\) atoms
= \(1.204 \times 10^{23}\)
\(\approxeq 1.2 \times 10^{23}\)
33.

The strength of metallic bonds depends on the

A. charge density of the atoms

B. ductility of the metal

C. number of valence electrons

D. total number of electrons in the atom

Detailed Solution

It is determined by the difference in the electron structures of the atoms. These primarily are: The number of outer electrons, i.e the number of valence shell electrons released during a metallic bond.
34.

When zinc is added to AgNO\(_{3}\) solution, crystals of silver forms on the zinc surface. This indicates that zinc is

A. oxidised

B. reduced

C. decomposed

D. dissociated

Detailed Solution

Reaction: \(2AgNO_{3} + Zn \to Zn(NO_{3})_{2} + 2Ag\)
The oxidation number of Zn in the reactant is 0, and in the product is +2. Therefor, it is oxidized.
35.

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. \(CuO_{4}\)

Detailed Solution

Cu : O
0.067 : 0.066
mole ratio \(\frac{0.067}{0.066}\) : \(\frac{0.066}{0.066}\)
= 1 : 1
= CuO
36.

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

Detailed Solution

The oxidation number of Iron in \(FeCl_{3}\) = +3. The oxidation number in \(FeCl_{2}\) = +2.
37.

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

A. Centrifugation

B. Filtration

C. Chromatography

D. Distillation

A
38.

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

B
39.

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

Detailed Solution

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
\(\frac{0.078}{0.07} : \frac{0.07}{0.07}\)
\(\approxeq 1:1\)
40.

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.

Detailed Solution

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.