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WAEC 2021 Chemistry | Objective

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Question 1 View Details

The hydrolysis of proteins by dilute mineral acids produces

A. sucrose

B. glucose

Correct C. amino acids

D. fatty acids

Correct Answer: C

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Question 2 View Details

Which of the following oxides causes acid rain?

A. CO

B. NO

Correct C. Causes \( \mathrm{NO}_{2} \)

Correct Answer: C

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Question 3 View Details

The ratio of carbon atoms to hydrogen atoms in a hydrocarbon is 1: 2. If its molecular mass is 56, what is its molecular formula?

Correct A. \( \mathrm{C}_{3} \mathrm{H}_{6} \)

B. C.H

C. \( \mathrm{C}_{2} \mathrm{H}_{4} \)

D. \( \mathrm{CH}_{2} \)

Correct Answer: A

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Question 4 View Details

What is the relative molecular mass of the compound below? \( [H=1.0 ; C=12.0 ; O=16.0] \)

A. 137

Correct B. 136

C. 64

D. 59

Correct Answer: B

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Question 5 View Details

Cathodic protection of metals is based on

A. standard electrode potential of hydrogen

B. its electrical conductivity

C. nature of oxides formed

Correct D. relative tendencies of oxidation

Correct Answer: D

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Question 6 View Details

If humid air is polluted by chlorine discharge, the air can be restored by sprinkling

A. solid \( \mathrm{MnO}_{2} \)

Correct B. acidified \( \mathrm{KMnO}_{4} \)

C. acidified \( \mathrm{FeSO}_{4} \)

D. saturated \( \mathrm{NaCl}_{(\mathrm{aq})} \)

Correct Answer: B

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Question 7 View Details

The alkanol represented by the structure below is

A. primary and dihydric

Correct B. secondary and monohydric

C. tertiary and dihydric

D. secondary and dihydric

Correct Answer: B

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Question 8 View Details

Which of the following pairs of compounds would form a precipitate when their aqueous solutions are mixed?

Correct A. NaCl and \( \mathrm{KNO}_{3} \)

B. KCl and \( \mathrm{NaNO}_{3} \)

C. \( \mathrm{K}_{2} \mathrm{SO}_{4} \) and \( \mathrm{BaCl}_{2} \)

D. \( \mathrm{NH}_{4} \mathrm{NO}_{3} \) and

Correct Answer: A

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Question 9 View Details

Which of the graphs illustrates the variation of the rate of evolution of a gas from a given length of magnesium ribbon ( \( y \)-axis) with increase in the concentration of the acid added ( \( x \)-axis)?

Correct A. I

B. II

C. III

D. IV

Correct Answer: A

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Question 10 View Details

Which of the graphs illustrates the variation of the pH of a given volume of strong acid solution ( \( y \)-axis) with the volume of strong base titrated against it?

Correct A. I

B. II

C. III

D. IV

Correct Answer: A

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Question 11 View Details

Which of the graphs illustrates the variation of the solubility of a salt in water ( \( y \)-axis) with increase in temperature ( \( x \)-axis), if the dissolution process is exothermic?

A. I

Correct B. III

C. III

D. IV

Correct Answer: B

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Question 12 View Details

The formation of ethene from dehydration of ethanol can be described as

A. an addition reaction

Correct B. an elimination reaction

C. an oxidation reaction

D. a substitution reaction

Correct Answer: B

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Question 13 View Details

Which of the following gases is highly soluble in water at room temperature?

Correct A. Ammonia

B. Carbon (IV) oxide

C. Chlorine

D. Nitrogen

Correct Answer: A

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Question 14 View Details

A molecule of phosphorus is

Correct A. diatomic

B. triatomic

C. tetraatomic

D. monoatomic

Correct Answer: A

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Question 15 View Details

The most common method of preparing insoluble salts is by

A. filtration

B. decomposition

C. neutralization

Correct D. double decomposition

Correct Answer: D

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Question 16 View Details

What number of moles of oxygen would exert a pressure of 10 atm at \( 320 K \) in an \( 8.2 d m^{3} \) cylinder? \( [R= \left.0.082 \mathrm{~atm} \mathrm{dm}^{3} \mathrm{~mol}^{-1} K^{-1}\right] \)

Correct A. 0.32

Correct Answer: A

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Question 17 View Details

The basic property of salts used as drying agents is

A. efflorescence

B. high melting point

Correct C. hygroscopy

D. low solubility

Correct Answer: C

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Question 18 View Details

What would be observed when aqueous ammonia is added in drops and then in excess to a solution of copper (II) ions?

Correct A. blue precipitate is formed which is soluble in excess ammonia

B. brick red precipitate is produced which is insoluble in excess ammonia

C. white precipitate is formed which is soluble in excess ammonia

D. green precipitate is formed which is insoluble in excess ammonia

Correct Answer: A

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Question 19 View Details

When \( \mathrm{CuSO}_{4 (\mathrm{aq})} \) is added to \( \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2 (\mathrm{aq})} \)

A. there would be no visible change

B. a blue precipitate would be formed

C. the resulting solution would become colourless

Correct D. a white precipitate would be formed

Correct Answer: D

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Question 20 View Details

How many carbon atoms does the parent chain contain?

A. 5

Correct B. 4

C. 3

D. 2

Correct Answer: B

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Question 21 View Details

Under which conditions of pressure \( (P) \) and temperature \( (T) \) would the volume of an inflated balloon increase?

A. both \( T \) and \( P \) are increased

B. \( T \) is increased and \( P \) are decreased

Correct C. \( T \) is increased and \( P \) is decreased

D. \( T \) is decreased and \( P \) is increased

Correct Answer: C

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Question 22 View Details

The collision between ideal gas molecules are considered to be perfectly elastic because

Correct A. they collide without losing energy

B. they move randomly in straight line

C. their average kinetic energy is variable

D. the distance between them is large compared to their sizes

Correct Answer: A

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Question 23 View Details

Elements with high ionization energies would

A. lose electrons easily

B. have large atomic radii

Correct C. have high effective nuclear charges

D. have low atomic numbers

Correct Answer: C

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Question 24 View Details

Which of the following statements about Group VII elements is correct?

A. They are present in the same physical state

B. They are strong reducing agents

Correct C. Their reactivity decreases down the group

D. They exist as monoatomic molecules

Correct Answer: C

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Question 25 View Details

Which of the following cell notations represent the diagram?

Correct A. \( \mathrm{B}^{2+} / \mathrm{B} / / \mathrm{A} / \mathrm{A}^{3+} \)

B. \( \mathrm{A}^{3+} / \mathrm{A} / / \mathrm{B}^{3} / \mathrm{B}^{2+} \)

C. \( \mathrm{B} / \mathrm{B}^{2+} / / \mathrm{A}^{3+} \)

D. \( \mathrm{A} / \mathrm{A}^{3+} / / \mathrm{B}^{2+} / \mathrm{B} \)

Correct Answer: A

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