International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

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What color change occurs when bromine is added to an aqueous solution of potassium iodide?

  1. Colourless to yellow

  2. Colourless to brown

  3. Brown to colorless

  4. Brown to yellow

The correct answer is: Colourless to brown

When bromine is added to an aqueous solution of potassium iodide, the solution changes from colorless to brown. This color change occurs because bromine is a brown-colored liquid that dissociates to produce bromine molecules in solution. The bromine molecules react with iodide ions present in the potassium iodide solution, resulting in the formation of bromide ions and iodine. As the reaction proceeds, the iodine gives the solution its characteristic brown color. In this case, the presence of iodine indicates a chemical change has occurred due to the redox reaction between the bromine and iodide ions, leading to the development of observable color in the solution. Thus, the correct answer reflects this fundamental aspect of the reaction involving the specific color associated with bromine and iodine in solution.