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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: ThetaPi on July 06, 2009, 05:45:38 AM

Title: Decolorization of bromine
Post by: ThetaPi on July 06, 2009, 05:45:38 AM

Problem. A few drops of aqueous bromine were added to a solution of iron (II) sulphate. The reddish-brown bromine was decolourised. The iron (II) sulphate turned from pale green to brown. Why is the reddish-brown bromine decolorized, and what causes the green iron (II) sulphate solution to turn brown?

Attempt. This is in my assignment on redox. I know that the reaction is not halogen displacement (besides, bromine would be a weak oxidizing agent in a halogen displacement reaction), metal displacement (bromine is not a metal), or hydrogen displacement (no hydrogen). I want to get an equation for the reaction. I know that after the reaction with bromine, there are Fe^(2+), SO_4^{2-} and Br^- ions.

Please help.

Title: Re: Decolorization of bromine
Post by: Astrokel on July 06, 2009, 06:07:34 AM

Fe²⁺ acts as a reducing agent.

Title: Re: Decolorization of bromine
Post by: ThetaPi on July 06, 2009, 06:18:26 AM

Quote from: Astrokel on July 06, 2009, 06:07:34 AM

Fe²⁺ acts as a reducing agent.

Then Br(aq) would be reduced to Br^-. Can we conclude directly from here that since Br^- is brown in color, therefore the final solution is brown?

Title: Re: Decolorization of bromine
Post by: Astrokel on July 06, 2009, 09:50:41 AM

Bromide is colourless. The brown colour is due to ferric sulphate formed.

Title: Re: Decolorization of bromine
Post by: ugbede on July 06, 2009, 05:32:46 PM

Simply exchange of ions. Fe+2 geen turn to brown Fe+3 and other.