Redox

Balancing redox

Quiz Type

Practice

Subject

Chemistry

Level

Level 100

Questions

10 questions

Created By

Lordina Atta-effah

Quick Rules

Time limit: 50 minutes
Multiple attempts are not allowed
All questions must be answered to submit

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Question 1 of 10

Question 1

Basic multiple choice Remembering

What does 'redox' refer to in chemistry?

A type of acid-base reaction

Reduction and oxidation reactions

Correct

Only oxidation reactions

Only reduction reactions

Explanation

Redox refers to processes that involve both reduction (gaining electrons) and oxidation (losing electrons) reactions occurring simultaneously.

Question 2

Basic multiple choice Remembering

In a redox reaction, which process involves the loss of electrons?

Reduction

Combustion

Oxidation

Correct

Synthesis

Explanation

Oxidation is defined as the process where a substance loses electrons during a chemical reaction.

Question 3

Basic multiple choice Understanding

What is the key characteristic of balancing a redox reaction?

Only balancing the number of atoms

Balancing charges and atoms

Correct

Ignoring electrons

Focusing only on the reactants

Explanation

Balancing a redox reaction requires ensuring that both the number of atoms and the total charge are equal on both sides of the reaction.

Question 4

Basic multiple choice Remembering

What is one common method used to balance redox reactions?

The addition of catalysts

Half-reaction method

Correct

Using only coefficients

Balancing by sight

Explanation

The half-reaction method involves breaking the overall redox reaction into separate oxidation and reduction half-reactions to balance them individually before combining them.

Question 5

Basic multiple choice Understanding

In balancing redox reactions, what role do electrons play?

They are not involved

They are only added to reactants

They are transferred between the oxidizing and reducing agents

Correct

They are simply ignored

Explanation

In redox reactions, electrons are transferred from the reducing agent (which is oxidized) to the oxidizing agent (which is reduced), which is essential for balancing the reaction.

Question 6

Complex multiple choice Understanding

In a redox reaction where substance A oxidizes substance B to form compound C, you are given the half-reactions: A → A^2+ + 2e⁻ (oxidation) and B + 2e⁻ → B^2- (reduction). If you were to balance the overall reaction, what steps would you take to ensure electron transfer is correctly aligned?

Ensure the number of electrons lost by A equals the electrons gained by B and then combine the half-reactions.

Correct

Combine the half-reactions first, then adjust the coefficients of A and B to balance the number of atoms.

Balance the charges on both sides before and after combining the half-reactions.

Only balance the oxidation half-reaction and leave the reduction half-reaction unadjusted.

Explanation

The correct approach is to ensure that the number of electrons lost by A equals the electrons gained by B before combining the half-reactions, as this reflects the conservation of charge and mass. The other options misrepresent critical steps in the process of balancing redox reactions.

Question 7

Complex multiple choice Understanding

Consider the following redox reaction: Zn + Cu^2+ → Zn^2+ + Cu. If you need to identify the oxidizing and reducing agents, how would you determine which substances are oxidized and reduced in this reaction?

Identify the changes in oxidation states: Zinc goes from 0 to +2 (oxidized), Copper goes from +2 to 0 (reduced). Thus, Zn is the reducing agent and Cu^2+ is the oxidizing agent.

Correct

Evaluate the reaction based on mass conservation principles; regardless of oxidation states, Copper must always be the reducing agent since it is a metal.

Assume that the substance with the higher initial oxidation number is always the oxidizing agent without checking oxidation states.

Only focus on the physical states of the reactants and products to determine the agents without considering oxidation states.

Explanation

The correct identification requires analyzing the changes in oxidation states, where Zinc is oxidized and thus is the reducing agent, while Copper(II) is reduced and serves as the oxidizing agent. The other options fail to apply proper principles in redox reactions.

Question 8

Case based multiple choice Understanding

[Case Scenario] In a laboratory, a student is conducting an experiment that involves the redox reaction between iron(III) ions and zinc. The student observes that the dark red solution of iron(III) ions turns colorless after adding zinc powder. The half-reaction for this involves the reduction of iron(III) ions to iron(II) ions and the oxidation of zinc to zinc ions. The student notes that the number of electrons transferred in the reaction is crucial for balancing the overall reaction. Question: What can the student conclude about the redox reaction observed in this experiment with respect to balancing redox reactions?

The reaction is balanced as it stands, without the need for further calculations.

The total number of electrons lost by zinc should be equal to the total number of electrons gained by iron(III) ions.

Correct

Adding more zinc will make the reaction reach equilibrium faster without changing the balance of electrons.

The reaction does not need to account for the charges of the ions present; balancing only considers the number of atoms.

Explanation

In a redox reaction, the principle of conservation of charge and mass must be adhered to by equating the number of electrons lost and gained. The student's observation indicates a genuine reduction and oxidation process, which together requires careful balancing to maintain the integrity of the reaction.

Question 9

Case based multiple choice Understanding

[Case Scenario] A chemistry class is working on balancing redox reactions. The teacher provides students with the unbalanced reaction between permanganate ion (MnO4^-) in acidic medium reacting with iron(II) ions (Fe^2+) to produce manganese(II) ions (Mn^2+) and Fe^3+ ions. The students need to determine how to balance the equation properly by balancing both half-reactions for oxidation and reduction. Question: Which step should the students take first in order to correctly balance the redox reaction in this scenario?

Identify and write the oxidation and reduction half-reactions separately.

Correct

Count the number of Mn and Fe ions in the unbalanced equation.

Combine all the species in the reaction into a single balanced equation immediately.

Ignore the charges on the ions since only the number of particles matters.

Explanation

To effectively balance redox reactions, the first critical step is to separate the half-reactions. Each must be balanced individually before combining them back into a full equation while ensuring that both mass and charge are conserved.

Question 10

Case based multiple choice Understanding

[Case Scenario] In a redox titration experiment, a chemist titrates a solution of potassium dichromate (K2Cr2O7) with a ferrous sulfate (FeSO4) solution. The endpoint of the titration is reached when the orange color of the dichromate ion disappears, indicating its reduction to green chromium(III) ions (Cr^3+). The chemist notes that balancing this reaction requires knowledge of charge, oxidation states, and stoichiometry. Question: How should the chemist approach balancing the redox reaction between potassium dichromate and ferrous sulfate?

Balance the reaction by first balancing the Cr atoms followed by the Fe atoms.

Determine the changes in oxidation states for all species involved and balance accordingly.

Correct

Ignore the stoichiometry and simply combine moles of reactants in equal amounts.

Only focus on the total number of atoms without considering oxidation states.

Explanation

Balancing redox reactions like that between potassium dichromate and ferrous sulfate involves determining the oxidation state changes for each component, allowing for an accurate representation of electron transfer, crucial for achieving a balanced equation.