What are the colours of bromine and iodine solutions in cyclohexane?

Bromine forms an orange solution.

Iodine forms a purple solution.

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Compare and explain the reactions of aqueous bromide ions with solutions of chlorine and iodine.

Aqueous bromide ions react with aqueous chlorine to produce a colour change to yellow due to the formation of bromine.

With iodine, there is no reaction observed because iodine is less reactive than bromine.

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What is the ionic equation for the reaction between iodide ions and bromine?

2I-(aq) + Br2(aq) ➔ I2(aq) + 2Br-(aq)

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State and explain the trend in reactivity of the halogens as we move down group 7.

The reactivity of halogens decreases as we move down group 7. 


This is because:

  1. As you go down the group, atomic radius and shielding increase (which outweighs the increased nuclear charge).
  2. This means there is a weaker electrostatic attraction between the nucleus and the electron it is trying to gain.
  3. This means more energy is required for a reaction to occur.

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What is a halogen displacement reaction?

A reaction in which a more reactive halogen displaces a less reactive halogen from a solution of its salt.

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What are the colours of bromine and iodine solutions in water?

Bromine forms a yellow solution.

Iodine forms an orange/brown solution.

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What is the ionic equation for the reaction between iodide ions and chlorine?

2I-(aq) + Cl2(aq) ➔ I2(aq) + 2Cl-(aq)

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