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Ch.4 - Reactions in Aqueous Solution
Chapter 4, Problem 58a

The following reactions (note that the arrows are pointing only one direction) can be used to prepare an activity series for the halogens:
Br2(aq) + 2 NaI(aq) → 2 NaBr(aq) + I2(aq)
Cl2(aq) + 2 NaBr(aq) → 2 NaCl(aq) + Br2(aq)
(a) Which elemental halogen would you predict is the most stable, upon mixing with other halides?

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Identify the reactions given: \( \text{Br}_2 + 2 \text{NaI} \rightarrow 2 \text{NaBr} + \text{I}_2 \) and \( \text{Cl}_2 + 2 \text{NaBr} \rightarrow 2 \text{NaCl} + \text{Br}_2 \).
Recognize that these reactions are single displacement reactions where a more reactive halogen displaces a less reactive halogen from its compound.
In the first reaction, \( \text{Br}_2 \) displaces \( \text{I}_2 \), indicating that \( \text{Br}_2 \) is more reactive than \( \text{I}_2 \).
In the second reaction, \( \text{Cl}_2 \) displaces \( \text{Br}_2 \), indicating that \( \text{Cl}_2 \) is more reactive than \( \text{Br}_2 \).
Conclude that \( \text{Cl}_2 \) is the most reactive and therefore the least stable when mixed with other halides, while \( \text{I}_2 \) is the least reactive and most stable.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Activity Series

The activity series is a list of elements organized by their ability to displace other elements in reactions. In the context of halogens, it ranks them based on their reactivity, with more reactive halogens able to displace less reactive ones from their compounds. Understanding this series helps predict the outcomes of reactions involving halogens.
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Activity Series Chart

Halogen Reactivity

Halogens are a group of elements in Group 17 of the periodic table, known for their high reactivity. Their reactivity decreases down the group, meaning fluorine is the most reactive, while iodine is the least. This trend is crucial for predicting which halogen will be more stable when mixed with other halides.
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Stability of Halides

The stability of halides refers to how likely a halogen is to remain in its ionic or molecular form when mixed with other halides. More reactive halogens tend to form less stable compounds with other halides, while less reactive halogens are more stable. This concept is essential for determining which halogen would be the most stable in a given reaction.
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