JEE Main 2023 — D And F Block Elements Question with Solution
From: JEE Main 2023 (Online) 29th January Evening Shift
Question
An indicator 'X' is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with at room temp. The indicator 'X' forms blue coloured complex with compound 'A' present in the solution. The indicator 'X' and compound 'A' respectively are :
Choose an option
Show full solutionCorrect option: D
Step-by-step explanation
The indicator 'X' is starch, and it forms a blue colored complex with iodine (compound 'A'). Therefore, the correct option is:
Option D: Starch and iodine
In this situation, starch is commonly used as an indicator to detect the presence of iodine because starch forms a deep blue complex with iodine. This color change is visible and helps in monitoring the progress of the reaction involving iodide ions and hydrogen peroxide, which ultimately produces iodine. The blue color indicates the presence of iodine in the solution.
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This is a previous-year question from JEE Main 2023, covering the D And F Block Elements chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.