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Practical Organic Chemistry question

2022 · 25 Jul · Shift 2 · Q13
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Practical Organic Chemistry question

2022 · 25 Jul · Shift 2 · Q13

JEE MainChemistryPractical Organic ChemistryMCQ+4 / −1
In base vs. acid titration, at the end point methyl orange is present as
  1. A
    quinonoid form
  2. B
    heterocyclic form
  3. C
    phenolic form
  4. D
    benzenoid form
View written solutionFree

Correct answer: A

  1. Identify the indicator and its color forms

    Methyl orange is an acid-base indicator. It exists in two structural forms depending on the medium:

    • In acidic medium: protonated quinonoid form (red)
    • In alkaline/basic medium: benzenoid form (yellow)

  2. Understand the titration mentioned

    The phrase "base vs. acid titration" means a base is being titrated against an acid, so at the end point with methyl orange, the solution passes through the indicator transition range near acidic side.

    Methyl orange changes color in the range approximately pH=3.1pH = 3.1pH=3.1 to 4.44.44.4.

  3. Form present at the end point

    At the end point for methyl orange, the indicator is taken to be in its acidic transition form, which is represented as the quinonoid form.

  4. Evaluate options

    • A: quinonoid form — Correct
    • B: heterocyclic form — Incorrect
    • C: phenolic form — Incorrect
    • D: benzenoid form — Incorrect for the endpoint in this context

  5. Final answer

    Therefore, the correct option is:

    A: quinonoid form\boxed{\text{A: quinonoid form}}A: quinonoid form​

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