Given below are two statements:
Statement I : Methyl orange is a weak acid.
Statement II : The benzenoid form of methyl orange is more intense/deeply coloured than the quinonoid form.
In the light of the above statement, choose the most appropriate answer from the options given below:

Solution

Chemistry ma’am · 4 steps

Methyl orange is the weak base of the pair, and its red quinonoid form is the deeper colour.

1. Statement I. In indicator theory, methyl orange is treated as a weak base, unlike phenolphthalein, which is a weak acid. It picks up H⁺ in acidic solution. That is why it is the indicator for strong acid against weak base titrations. So Statement I is incorrect.
2. Two forms. Quinonoid theory says an indicator exists in two forms with different colours. For methyl orange, the form you see depends on whether the solution is basic or acidic.

   Form	Where it exists	Colour	Intensity
   Benzenoid	basic medium	yellow	lighter
   Quinonoid	acidic medium (protonated)	red	deeper, more intense

3. Statement II. The quinonoid structure has more extended conjugation, so it absorbs visible light more strongly and looks deeper. Statement II has this reversed, so it is incorrect.
4. So. Both statements are incorrect, which is option (a).

The idea to keep. Remember the pair: phenolphthalein is a weak acid and methyl orange is a weak base. In quinonoid theory, the quinonoid form is always the deeper-coloured one.

Answer from the NTA final answer key. Solution by PrepWiser.