2.7: Understand How Displacement Reactions involving Halogens and Halides Provide Evidence for the Trend in Reactivity in Group 7

HALOGENS: Group 7 Non-Metals that are poisonous and commonly includes Chlorine, Bromine and Iodine

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DISPLACEMENT REACTIONS

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DISPLACEMENT REACTION: When a more reactive Halogen displaces a less reactive Halogen for an Aqueous Solution of its Halide

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• Reactivity of Group 7 Non-Metals increases as you go up the Group
• Out of the 3 Halogens - Chlorine, Bromine and Iodine - Chlorine is the most reactive and iodine is the least reactive

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AQUEOUS SOLUTION COLOUR OF HALOGENS:

AQUEOUS SOLUTION	COLOUR
CHLORINE	Very pale green, but usually appears colourless as it is dilute
BROMINE	Orange but will turn yellow when diluted
IODINE	Brown

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Examples:

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Chlorine is above Bromine in Group 7 so is more reactive. Chlorine will therefore displace Bromine from an Aqueous Solution of Metal Bromide:

Chlorine  +  Potassium Bromide Solution  →  Potassium Chloride Solution  +  Bromine

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Chlorine is also above Iodine in Group 7 so is more reactive. Chlorine will therefore displace Iodine from an Aqueous Solution of Metal Iodide:

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Chlorine  +  Sodium Iodide Solution  →  Sodium Chloride Solution  +  Iodine

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Bromine is above Iodine in Group 7 so is more reactive. Bromine will therefore displace Iodine from an Aqueous Solution of Metal Iodide:

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Bromine  +  Magnesium Iodide Solution  →  Magnesium Bromide Solution  +  Iodine