Chemistry: Oxidation and Reduction Concepts
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Questions and Answers

What occurs during the oxidation of magnesium?

  • It loses neutrons.
  • It gains protons.
  • It gains electrons.
  • It loses electrons. (correct)

A reducing agent is always oxidized during a chemical reaction.

True (A)

What is the term used for a substance that brings about oxidation in other substances?

oxidising agent

During redox reactions, oxidation is associated with the ______ of electrons.

<p>loss</p> Signup and view all the answers

Match the following elements with their roles in a redox reaction:

<p>Zn = Reducing agent Cu^2+ = Oxidising agent Cl<del>2</del> = Oxidising agent Mg = Reducing agent</p> Signup and view all the answers

What does the acronym OILRIG stand for?

<p>Oxidation Is Loss, Reduction Is Gain (A)</p> Signup and view all the answers

In a redox reaction, oxidation and reduction can occur independently of each other.

<p>False (B)</p> Signup and view all the answers

Each sodium atom loses one electron and each chlorine atom gains one electron in the formation of ______.

<p>sodium chloride</p> Signup and view all the answers

What is the oxidation number of sulfur in Na2S2O3?

<p>+2 (B)</p> Signup and view all the answers

The oxidation number of nitrogen in the NO3^- ion is -5.

<p>False (B)</p> Signup and view all the answers

What rule does oxygen generally follow regarding its oxidation number?

<p>-2</p> Signup and view all the answers

In oxidized species, the oxidation number (______/decreases).

<p>increases</p> Signup and view all the answers

What is the general oxidation state of hydrogen in its compounds?

<p>+1 (D)</p> Signup and view all the answers

The sum of oxidation numbers in a compound must equal the total charge of that compound if it is a complex ion.

<p>True (A)</p> Signup and view all the answers

What oxidation number is assigned to halogens in compounds with more electronegative atoms?

<p>Positive</p> Signup and view all the answers

Which substance acts as the reducing agent in the given reaction?

<p>Copper (B)</p> Signup and view all the answers

Match each element to its typical oxidation number:

<p>Oxygen = -2 Hydrogen = +1 Sodium = +1 Nitrogen in NO3^- = +5</p> Signup and view all the answers

Chlorine displaces bromine from a bromide salt solution.

<p>True (A)</p> Signup and view all the answers

What color does the potassium iodide solution turn when chlorine water is added?

<p>reddish-brown</p> Signup and view all the answers

In the reaction between sodium sulfite and chlorine water, _____ ion is present when barium chloride is added.

<p>sulfate</p> Signup and view all the answers

Match the following elements with their role:

<p>Chlorine = Oxidizing agent Copper = Reducing agent Bromine = Displaces iodine Sodium sulfite = Remains unchanged</p> Signup and view all the answers

What is the oxidation state of sulfur in sulfuric acid?

<p>+6 (B)</p> Signup and view all the answers

The reaction produces I2 when potassium iodide is mixed with bromine water.

<p>True (A)</p> Signup and view all the answers

What color does the potassium bromide solution turn when chlorine is added?

<p>yellow/orange</p> Signup and view all the answers

What is the product of the oxidation of iron(II) ions in the presence of chlorine?

<p>Fe^3+ (B)</p> Signup and view all the answers

A greenish-brown precipitate indicates the presence of Fe^2+ ions.

<p>False (B)</p> Signup and view all the answers

What color does the copper sulfate solution become when magnesium is added?

<p>Colorless</p> Signup and view all the answers

When Zn displaces Cu^2+, the resulting metal coating on zinc is ______.

<p>copper</p> Signup and view all the answers

Match the following reactions to their outcomes:

<p>Oxidation of Fe^2+ = Formation of Fe^3+ Reduction of Cl2 = Formation of Cl^- Displacement of Cu by Zn = Coating of Zn with Cu Displacement of Cu by Mg = Color change from blue to colorless</p> Signup and view all the answers

What half-reaction represents the oxidation of iron(II) ions?

<p>Fe^2+ → Fe^3+ + e^- (B)</p> Signup and view all the answers

What is the oxidation number change of aluminum in the reaction 8Al + 3Fe3O4 → 4Al2O3 + 9Fe?

<p>0 to +3 (B)</p> Signup and view all the answers

In the reaction Cd + H^+ + NO3^-- → Cd^2+ + NO + H2O, Cd acts as the oxidizing agent.

<p>False (B)</p> Signup and view all the answers

Zinc has a lower tendency to lose electrons than copper.

<p>False (B)</p> Signup and view all the answers

What is the reducing agent in the reaction 8Al + 3Fe3O4 → 4Al2O3 + 9Fe?

<p>Al</p> Signup and view all the answers

The balanced half-equation for the reduction of permanganate ions shows that MnO4^- requires ______ electrons to become Mn^2+.

<p>5</p> Signup and view all the answers

In the equation Mn O4^- + 5Fe^2+ + 8H^+ → Mn^2+ + 5Fe^3+ + ______, the product formed is water.

<p>H<del>2</del>O</p> Signup and view all the answers

Match the following species with their roles in the given reactions:

<p>Mn O<del>4</del>^- = Oxidizing agent NO<del>3</del>^- = Oxidizing agent Fe^2+ = Reducing agent Al = Reducing agent</p> Signup and view all the answers

Flashcards

Oxidation

Loss of electrons by an element

Reduction

Gain of electrons by an element

Redox Reaction

A reaction where oxidation and reduction occur simultaneously.

Oxidising agent

A substance that causes another substance to lose electrons (be oxidized).

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Reducing agent

A substance that causes another substance to gain electrons (be reduced).

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Oxidation number

The charge an atom appears to have in a compound, calculated using rules.

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Example of redox reaction

The reaction between sodium and chlorine to produce sodium chloride (NaCl).

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Chlorine's role in water treatment

Chlorine oxidises chemicals in germs, killing them and disinfecting water.

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Oxidation Number of an Element

A number assigned to an element in a compound or ion that represents its degree of oxidation or reduction, reflecting its ability to gain or lose electrons.

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Oxidation Number of Oxygen (General)

-2. In peroxides & OFâ‚‚ it's an exception to this rule.

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Oxidation Number of Hydrogen (General)

+1. But in metal hydrides, it is -1.

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Oxidation Number Rules in Compounds

The sum of the oxidation numbers of all elements in a neutral compound is zero, and in an ion, the sum must match the charge of the ion.

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Oxidation Number of Halogens

-1. Except if bonded with a more electronegative element.

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Calculating Oxidation Numbers

Determine unknown oxidation numbers from a given compound or ion by setting up an equation, using known oxidation numbers and balancing with the overall charge of the substance/ion.

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Halogens' Oxidizing Ability

Halogens higher in the group (e.g., chlorine) oxidize halogens lower in the group (e.g., bromine).

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Chlorine's Oxidizing Power

Chlorine can displace bromine and iodine from their salts, demonstrating its strong oxidizing ability.

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Sulfate Formation

Chlorine does not directly affect sulfite, but reaction with barium chloride forms a sulfate precipitate.

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Halogen Displacement

Stronger halogens displace weaker halogens from their salts in solution.

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Oxidation of Iron(II) sulfate

Iron(II) sulfate (FeSO4) undergoing oxidation by chlorine water, forming Iron (III) ions

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Reduction of Chlorine

Chlorine(Cl2) gaining electrons to form chloride ions (Cl-)

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Displacement Reaction (Zinc)

Zinc (Zn) displacing copper (Cu) from copper sulfate solution

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Displacement Reaction (Magnesium)

Magnesium (Mg) displacing copper (Cu) from copper sulfate solution

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Balancing Redox Equations

Using oxidation numbers to balance chemical equations involving electron transfer

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Half-reaction (Oxidation)

A reaction showing the loss or gain of electrons of a substance

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Half-reaction (Reduction)

A reaction showing the gaining of electrons of a substance

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Balancing Redox Reactions

Balancing chemical equations involving oxidation and reduction reactions ensuring all atoms and charges are equal on both sides.

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Redox Reaction (Example)

The reaction between Cadmium (Cd) and Nitric Acid (HNO3) to produce Cadmium ions (Cd2+), Nitric Oxide (NO) and water (H2O).

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Study Notes

Oxidation and Reduction

  • Oxidation: Loss of electrons
  • Reduction: Gain of electrons
  • OILRIG: Oxidation is Loss, Reduction is Gain
  • Redox reactions: Oxidation and reduction always occur together
  • Oxidising agent: Substance that brings about oxidation in other substances.
  • Reducing agent: Substance that brings about reduction in other substances.

Oxidation Numbers

  • Oxidation number: Charge that an atom has or appears to have when electrons are distributed according to rules.
  • Oxidation numbers are used for tracking electrons in chemical reactions, especially in covalent compounds.
  • Rules for assigning oxidation numbers:
    • Uncombined element = 0
    • Ion of an element = charge of the ion
    • Oxygen = -2 (except in peroxides and OF2)
    • Hydrogen = +1 (except in metal hydrides)
    • Halogens = -1 (except when bonded to a more electronegative atom)
    • Sum of oxidation numbers in a neutral compound = 0
    • Sum of oxidation numbers in a polyatomic ion = charge of the ion

Oxidation and Reduction in Terms of Oxidation Numbers

  • Oxidation: Increase in oxidation number
  • Reduction: Decrease in oxidation number
  • Oxidising agent: The substance that is reduced.
  • Reducing agent: The substance that is oxidized.

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Oxidation and Reduction PDF

Description

Explore the fundamental concepts of oxidation and reduction in chemistry. This quiz focuses on the definitions, rules for oxidation numbers, and the relationship between oxidizing and reducing agents. Test your knowledge and understanding of these critical chemical principles.

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