Chapter 4: Problem 17
Identify what is being oxidized and reduced in this redox equation by assigning oxidation numbers to the atoms. $$ 2 \mathrm{KrF}_{2}+2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{Kr}+4 \mathrm{HF}+\mathrm{O}_{2} $$
Short Answer
Expert verified
Kr is reduced; O in Hâ‚‚O is oxidized.
Step by step solution
01
Assign Oxidation Numbers to Elements in Reactants
Assign oxidation numbers to all elements in the reactants. \( \mathrm{KrF}_{2} \): \( \mathrm{Kr} \) is \(+4\), \( \mathrm{F} \) is \(-1\), \( \mathrm{H}_{2} \mathrm{O} \): \( \mathrm{H} \) is \(+1\), \( \mathrm{O} \) is \(-2\).
02
Assign Oxidation Numbers to Elements in Products
Assign oxidation numbers to all elements in the products. \( \mathrm{Kr} \) remains \(0\), \( \mathrm{HF} \): \( \mathrm{H} \) is \(+1\), \( \mathrm{F} \) is \(-1\), \( \mathrm{O}_{2} \): \( \mathrm{O} \) is \(0\).
03
Identify Changes in Oxidation Numbers
Compare the oxidation numbers from reactants to products. \( \mathrm{Kr} \) changes from \(+4\) to \(0\); \( \mathrm{O} \) changes from \(-2\) in \( \mathrm{H}_{2} \mathrm{O} \) to \(0\) in \( \mathrm{O}_{2} \).
04
Determine Oxidized and Reduced Elements
Identify which elements gain or lose electrons. \( \mathrm{Kr} \) is reduced because its oxidation number decreases from \(+4\) to \(0\). \( \mathrm{O} \) is oxidized because its oxidation number increases from \(-2\) to \(0\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Oxidation Numbers
In the study of chemistry, oxidation numbers are a helpful tool for tracking the transfer of electrons in oxidation-reduction (redox) reactions. An oxidation number assigns a charge to an atom assuming electronegativity fully involves electrons, whether bonding or not.
To assign these numbers, remember these rules:
To assign these numbers, remember these rules:
- The oxidation number of an uncombined element is always 0.
- For ions, the oxidation number equals the ion's charge.
- In compounds, hydrogen typically has an oxidation number of +1, while oxygen often has -2.
- Fluorine, being highly electronegative, always carries an oxidation number of -1 in its compounds.
- In neutral substances, the sum of oxidation numbers of all atoms must equal 0. For polyatomic ions, it equals the ion’s charge.
Electron Transfer
Electron transfer is a fundamental concept in redox reactions, essential for understanding the movement of electrons between reactants and products. In a redox reaction, transfer of electrons from one substance to another defines the process.
Consider what really happens when an atom changes its oxidation state:
Consider what really happens when an atom changes its oxidation state:
- Oxidation occurs when an atom or molecule loses electrons. This process increases its oxidation number.
- Reduction occurs when an atom or molecule gains electrons, decreasing its oxidation number.
- Krypton (Kr) gains electrons, moving its oxidation state from +4 in KrF extsubscript{2} to 0 as Kr. This represents the reduction of Kr.
- Meanwhile, oxygen (O) loses electrons as it transitions from -2 in H extsubscript{2}O to 0 in O extsubscript{2}, signifying its oxidation.
Redox Equations
Redox equations offer a clear representation of redox reactions, where one species undergoes oxidation and another undergoes reduction. These reactions play a critical role in various chemical and biological processes.
In balancing redox equations:
- **Krypton (Kr)** undergoes reduction, as seen by the decrease in oxidation number. - **Oxygen (O)** is oxidized, with its oxidation number increasing.
This equation illustrates the essential balance needed for accurate depiction of the electron flow in chemical reactions.
In balancing redox equations:
- Identify the species that get oxidized and reduced by determining changes in oxidation numbers.
- Ensure that the electrons lost in the oxidation process are equal to those gained during reduction.
- The equation often includes both half-reactions showing oxidation and reduction separately before combining them into the overall balanced equation.
- **Krypton (Kr)** undergoes reduction, as seen by the decrease in oxidation number. - **Oxygen (O)** is oxidized, with its oxidation number increasing.
This equation illustrates the essential balance needed for accurate depiction of the electron flow in chemical reactions.