Detection of Bromide Anion in Sodium Bromide Salt

Main Experiment

• Objective: To detect bromide anion in sodium bromide salt.
• Reagent Used: Concentrated sulfuric acid.
• Procedure:
  1. Add drops of concentrated sulfuric acid to sodium bromide salt.
  2. Observe the changes.
• Observations:
  • Effervescence occurs due to the evolution of hydrogen bromide gas, which is colorless.
  • Hydrogen bromide gas is partially oxidized by sulfuric acid.
  • Orange-red fumes of bromine are released.
  • Heating increases the release of bromine fumes.
  • Bromine fumes turn a paper wetted with starch into yellow.

Confirmatory Experiment

• Objective: To confirm the presence of bromide anion.
• Reagents Used:
  • Distilled water
  • Silver nitrate solution
  • Concentrated ammonia solution
• Procedure:
  1. Add a small amount of sodium bromide salt to a clean test tube.
  2. Add distilled water and shake to form a salt solution.
  3. Add silver nitrate solution to the salt solution.
  4. Observe the changes.
  5. Add concentrated ammonia solution to the formed precipitate.
  6. Observe the changes.
• Observations:
  • A white-yellowish precipitate of silver bromide is formed when silver nitrate solution is added.
  • The precipitate slowly dissolves in concentrated ammonia solution.

Summary

• Adding concentrated sulfuric acid to sodium bromide salt produces reddish-orange bromine fumes, turning starch-wetted paper yellow.
• Adding silver nitrate to sodium bromide solution forms a white-yellowish silver bromide precipitate, which dissolves slowly in concentrated ammonia.