IB Chemistry Topic R3.2.2 Redox Half-equations Revision Notes (SL/HL)

IB Chemistry Topic R3.2.2 Redox Half-equations Revision Notes (SL/HL) | RevisionDojo

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What Are Half-Equations, and Why Do We Use Them?

Definition

Half-equation in a redox reaction

A half-equation focuses on one part of a redox reaction: either the oxidation or reduction process.

By breaking a redox reaction into these two components, we can better track the movement of electrons.

Example

Let’s take the reaction between zinc and copper(II) sulfate as an example:
Full Reaction: $$
\text{Zn}(s) + \text{Cu}^{2+}(aq) \to \text{Zn}^{2+}(aq) + \text{Cu}(s)
$$
This reaction involves two simultaneous processes:
- Zinc metal ($\text{Zn}$) is oxidized to form zinc ions ($\text{Zn}^{2+}$).
- Copper ions ($\text{Cu}^{2+}$) are reduced to form copper metal ($\text{Cu}$).

A Step-by-Step Method for Half-Equations

Identify the species being oxidized and reduced:
1. Oxidation: The species losing electrons.
2. Reduction: The species gaining electrons.
Write the unbalanced equation for each process:
1. For oxidation, place the electrons ($e^-$) on the right-hand side of the equation.
2. For reduction, place the electrons ($e^-$) on the left-hand side.
Balance the atoms:
1. Ensure the number of atoms of each element is the same on both sides of the equation.
Balance the charges:
1. Add electrons to one side of the equation to balance the overall charge.

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What Are Half-Equations, and Why Do We Use Them?

Definition

Half-equation in a redox reaction

A half-equation focuses on one part of a redox reaction: either the oxidation or reduction process.

By breaking a redox reaction into these two components, we can better track the movement of electrons.

Example

Let’s take the reaction between zinc and copper(II) sulfate as an example:
Full Reaction: $$
\text{Zn}(s) + \text{Cu}^{2+}(aq) \to \text{Zn}^{2+}(aq) + \text{Cu}(s)
$$
This reaction involves two simultaneous processes:
- Zinc metal ($\text{Zn}$) is oxidized to form zinc ions ($\text{Zn}^{2+}$).
- Copper ions ($\text{Cu}^{2+}$) are reduced to form copper metal ($\text{Cu}$).

A Step-by-Step Method for Half-Equations

Identify the species being oxidized and reduced:
1. Oxidation: The species losing electrons.
2. Reduction: The species gaining electrons.
Write the unbalanced equation for each process:
1. For oxidation, place the electrons ($e^-$) on the right-hand side of the equation.
2. For reduction, place the electrons ($e^-$) on the left-hand side.
Balance the atoms:
1. Ensure the number of atoms of each element is the same on both sides of the equation.
Balance the charges:
1. Add electrons to one side of the equation to balance the overall charge.

Definition

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Note

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Excepteur sint occaecat cupidatat non proident

Tip

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Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

IB Chemistry R3.2.2 Redox Half-equations Notes

Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

What Are Half-Equations, and Why Do We Use Them?

A Step-by-Step Method for Half-Equations

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Duis aute irure dolor in reprehenderit

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What Are Half-Equations, and Why Do We Use Them?

A Step-by-Step Method for Half-Equations

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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