ACE Your Redox Reactions
One of the ways we discovered to know if a redox reaction has occurred, you will find that the oxidation numbers of two elements has changed from the reactant side to the product side an example is the formation of hydrogen fluoride. This quiz will test your understanding of redox reactions, including oxidizing and reducing agents. Give it a try and ace your redox reactions test.
Questions and Answers
- 1.
Which change is oxidation?
- A.
Gain of electrons
- B.
Gain of hydrogen
- C.
Loss of oxygen
- D.
Loss of electrons
Correct Answer
D. Loss of electronsExplanation
Oxidation is defined as the loss of electrons from an atom, ion, or molecule. In this context, the correct answer is "loss of electrons." When an atom or molecule loses electrons, it becomes more positively charged, indicating an oxidation process. Conversely, gain of electrons is known as reduction, which is the opposite of oxidation. The other options, gain of hydrogen and loss of oxygen, are not directly related to oxidation.Rate this question:
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- 2.
Which change is reduction?
- A.
A decrease in oxidation state
- B.
Gain of oxygen
- C.
Loss of electrons
- D.
Loss of hydrogen
Correct Answer
A. A decrease in oxidation stateExplanation
A decrease in oxidation state is considered a reduction because it involves the gain of electrons, which is a characteristic of reduction reactions. When an atom or molecule undergoes a decrease in oxidation state, it is gaining electrons and becoming more negatively charged. This gain of electrons is associated with a reduction in the overall oxidation state of the atom or molecule. Therefore, a decrease in oxidation state is a reduction.Rate this question:
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- 3.
What is the oxidation state of chromium in the oxide CrO3?
- A.
+3
- B.
-3
- C.
+6
- D.
-6
Correct Answer
C. +6Explanation
The oxidation state of an element is a measure of the number of electrons it has gained or lost in a compound. In the oxide CrO3, there are three oxygen atoms, each with an oxidation state of -2. Since the overall charge of the compound is 0, the oxidation state of chromium (Cr) must be such that the sum of the oxidation states of all the atoms equals 0. By solving the equation 3(-2) + x = 0, we find that x = +6. Therefore, the oxidation state of chromium in CrO3 is +6.Rate this question:
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- 4.
Magnesium displaces lead ions from a solution of lead(II) sulphate. Which statement about this reaction is true?
- A.
Lead (II) ions are oxidized.
- B.
Magnesium atoms are oxidised.
- C.
Lead (II) ions lose electrons.
- D.
Magnesium atoms gain electrons .
Correct Answer
B. Magnesium atoms are oxidised.Explanation
In this reaction, magnesium displaces lead ions from the lead(II) sulphate solution. This means that magnesium is undergoing a redox reaction where it is being oxidized, since it is losing electrons in order to displace the lead ions. Therefore, the statement "Magnesium atoms are oxidised" is true.Rate this question:
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- 5.
Which one of the following substances is a reducing agent?
- A.
Argon
- B.
Oxygen
- C.
Carbon dioxide
- D.
Carbon monoxide
Correct Answer
D. Carbon monoxideExplanation
Carbon monoxide is a reducing agent because it has a tendency to donate electrons to other substances. In a redox reaction, carbon monoxide can oxidize another substance by giving up electrons, while itself getting reduced. This is due to the presence of a polar covalent bond between carbon and oxygen, where oxygen is more electronegative and attracts the electron density towards itself, creating a partial positive charge on carbon. This makes carbon monoxide a good reducing agent.Rate this question:
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- 6.
Which compound, when added to aqueous iron(II) sulphate, takes part in a redox reaction?
- A.
Ammonia
- B.
Barium chloride
- C.
Acidified potassium manganate (VII)
- D.
Sodium hydroxide
Correct Answer
C. Acidified potassium manganate (VII)Explanation
Acidified potassium manganate (VII) is the compound that takes part in a redox reaction when added to aqueous iron(II) sulphate. This is because potassium manganate (VII) is a strong oxidizing agent and can oxidize iron(II) ions to iron(III) ions. In this reaction, the manganese in potassium manganate (VII) is reduced from +7 oxidation state to +2 oxidation state, while the iron in iron(II) sulphate is oxidized from +2 oxidation state to +3 oxidation state. Therefore, a redox reaction occurs between the two compounds.Rate this question:
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- 7.
Acidified potassium dichromate (VI) can be used to detect the presence of ethanol vapour in the breath of a person who consumed alcohol. A colour change from orange to green is observed if ethanol is present.This shows that ethanol is
- A.
An alkali
- B.
An indicator
- C.
An oxidising agent
- D.
A reducing agent
Correct Answer
D. A reducing agentExplanation
The correct answer is "a reducing agent." When acidified potassium dichromate (VI) is used to detect the presence of ethanol vapor, a color change from orange to green occurs. This color change indicates that ethanol is a reducing agent, as it causes the dichromate ion (Cr2O7 2-) in the potassium dichromate solution to be reduced to the green chromium(III) ion (Cr3+). Therefore, ethanol has the ability to donate electrons and cause a reduction reaction to occur.Rate this question:
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- 8.
What is the oxidation state of sulphur in SO32-
- A.
-4
- B.
-2
- C.
+2
- D.
+4
- E.
+6
Correct Answer
D. +4Explanation
The oxidation state of an element in a compound is a measure of the charge that element would have if all the shared electrons were assigned to the more electronegative atom. In SO32-, the oxidation state of oxygen is -2. Since the overall charge of the ion is -2, the sum of the oxidation states of all the atoms must equal -2. Therefore, the oxidation state of sulfur can be determined by solving the equation: x + 3(-2) = -2, where x is the oxidation state of sulfur. Solving this equation gives x = +4, indicating that the oxidation state of sulfur in SO32- is +4.Rate this question:
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- 9.
In which reaction is the first substance acting as a reducing agent?
- A.
Chlorine + iron(II) chloride ---> iron(III) chloride
- B.
Copper(II) oxide + hydrogen ---> copper + water
- C.
Hydrochloric acid + magnesium oxide ---> magnesium chloride + water
- D.
Carbon monoxide + zinc oxide ---> zinc + carbon dioxide
Correct Answer
D. Carbon monoxide + zinc oxide ---> zinc + carbon dioxideExplanation
In the reaction "carbon monoxide + zinc oxide ---> zinc + carbon dioxide", carbon monoxide is acting as a reducing agent. This is because carbon monoxide is oxidized (loses electrons) while zinc oxide is reduced (gains electrons). The carbon monoxide transfers electrons to the zinc oxide, causing the reduction of zinc oxide to zinc and the oxidation of carbon monoxide to carbon dioxide.Rate this question:
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- 10.
Hydrogen peroxide, H2O2, reacts with silver oxide according to the following equation.Ag2O(s) + H2O2(l) ---> 2Ag(s) + H2O(l) + O2(g)In this reaction, hydrogen peroxide behaves as
- A.
An acid
- B.
A catalyst
- C.
A dehydrating agent
- D.
An oxidising agent
- E.
A reducing agent
Correct Answer
E. A reducing agentExplanation
In this reaction, hydrogen peroxide (H2O2) is acting as a reducing agent. A reducing agent is a substance that donates electrons to another substance, causing it to be reduced (gain electrons). In the given reaction, the hydrogen peroxide (H2O2) is being oxidized (loses electrons) to form water (H2O) and oxygen gas (O2). The silver oxide (Ag2O) is being reduced (gains electrons) to form silver metal (Ag). Therefore, hydrogen peroxide is behaving as a reducing agent in this reaction.Rate this question:
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Quiz Review Timeline +
Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.
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Current Version
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Mar 21, 2023Quiz Edited by
ProProfs Editorial Team -
Jan 29, 2010Quiz Created by
Davincent
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