WAEC Chemistry questions

357 questions with answers and explanations. Tap an option to check yourself.

All topics Acids, bases and salts · 26 Air · 16 Atomic structure and bonding · 26 Chemical combination · 27 Chemical equilibrium · 16 Chemistry and industry · 17 Electrolysis · 19 Energy changes · 16 Environmental pollution · 15 Kinetic theory of matter and gas laws · 18 Metals and their compounds · 23 Non-metals and their compounds · 22 Organic compounds · 29 Oxidation and reduction · 19 Rates of chemical reaction · 16 Separation of mixtures and purification · 18 Solubility · 16 Water · 18

Question 281· Oxidation and reduction· WAEC
In the change Fe²⁺ → Fe³⁺ + e⁻, the iron(II) ion is
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Answer: B. oxidised
Explanation and discussion
Question 282· Oxidation and reduction· WAEC
Find the oxidation number of manganese in KMnO₄.
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Answer: B. +7
Explanation and discussion
Question 283· Oxidation and reduction· WAEC
Hydrogen sulphide gas is a good
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Answer: D. reducing agent
Explanation and discussion
Question 284· Oxidation and reduction· WAEC
The oxidation number of nitrogen in NH₃ is
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Answer: B. −3
Explanation and discussion
Question 285· Oxidation and reduction· WAEC
In terms of electron transfer, oxidation is the
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Answer: B. loss of electrons
Explanation and discussion
Question 286· Oxidation and reduction· WAEC
Oxidation in terms of oxidation number is
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Answer: C. an increase in oxidation number
Explanation and discussion
Question 287· Oxidation and reduction· WAEC
An oxidising agent
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Answer: A. gains electrons
Explanation and discussion
Question 288· Oxidation and reduction· WAEC
Zinc dust added to blue copper(II) tetraoxosulphate(VI) solution reacts as Zn + Cu²⁺ → Zn²⁺ + Cu. Which species is reduced?
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Answer: A. the copper(II) ion
Explanation and discussion
Question 289· Oxidation and reduction· WAEC
In the reaction 2Mg + O₂ → 2MgO, the reducing agent is
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Answer: A. magnesium
Explanation and discussion
Question 290· Rates of chemical reaction· WAEC
Which of the following increases the rate of reaction between marble and dilute hydrochloric acid?
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Answer: D. Using powdered marble
Explanation and discussion
Question 291· Rates of chemical reaction· WAEC
Hydrogen peroxide decomposes faster when manganese(IV) oxide is added. The manganese(IV) oxide
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Answer: B. is a catalyst and is unchanged at the end
Explanation and discussion
Question 292· Rates of chemical reaction· WAEC
Powdered marble reacts faster with dilute acid than marble chips of the same mass because the powder
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Answer: C. has a larger surface area
Explanation and discussion
Question 293· Rates of chemical reaction· WAEC
The rate of a reaction can be followed by measuring
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Answer: C. the volume of gas given off over time
Explanation and discussion
Question 294· Rates of chemical reaction· WAEC
For many reactions, a 10 °C rise in temperature roughly
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Answer: A. doubles the rate
Explanation and discussion
Question 295· Rates of chemical reaction· WAEC
A catalyst speeds up a reaction by
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Answer: B. providing a pathway with lower activation energy
Explanation and discussion
Question 296· Rates of chemical reaction· WAEC
Which apparatus is suitable for following the rate of a reaction that gives off a gas?
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Answer: D. a gas syringe and a stop-clock
Explanation and discussion
Question 297· Rates of chemical reaction· WAEC
Increasing temperature increases reaction rate mainly because
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Answer: A. more particles have energy above the activation energy
Explanation and discussion
Question 298· Rates of chemical reaction· WAEC
Which of these will increase the rate of reaction between calcium trioxocarbonate(IV) and dilute hydrochloric acid?
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Answer: B. using powdered calcium trioxocarbonate(IV)
Explanation and discussion
Question 299· Rates of chemical reaction· WAEC
Manganese(IV) oxide speeds up the decomposition of hydrogen peroxide. It acts as
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Answer: B. a catalyst
Explanation and discussion
Question 300· Rates of chemical reaction· WAEC
A catalyst speeds up a chemical reaction by
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Answer: C. lowering the activation energy
Explanation and discussion

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WAEC Chemistry questions

In the change Fe²⁺ → Fe³⁺ + e⁻, the iron(II) ion is

Find the oxidation number of manganese in KMnO₄.

Hydrogen sulphide gas is a good

The oxidation number of nitrogen in NH₃ is

In terms of electron transfer, oxidation is the

Oxidation in terms of oxidation number is

An oxidising agent

Zinc dust added to blue copper(II) tetraoxosulphate(VI) solution reacts as Zn + Cu²⁺ → Zn²⁺ + Cu. Which species is reduced?

In the reaction 2Mg + O₂ → 2MgO, the reducing agent is

Which of the following increases the rate of reaction between marble and dilute hydrochloric acid?

Hydrogen peroxide decomposes faster when manganese(IV) oxide is added. The manganese(IV) oxide

Powdered marble reacts faster with dilute acid than marble chips of the same mass because the powder

The rate of a reaction can be followed by measuring

For many reactions, a 10 °C rise in temperature roughly

A catalyst speeds up a reaction by

Which apparatus is suitable for following the rate of a reaction that gives off a gas?

Increasing temperature increases reaction rate mainly because

Which of these will increase the rate of reaction between calcium trioxocarbonate(IV) and dilute hydrochloric acid?

Manganese(IV) oxide speeds up the decomposition of hydrogen peroxide. It acts as

A catalyst speeds up a chemical reaction by