Compound that will give positive Lassaigne's test for both nitrogen and halogen is :

Given below are two statements: one is labelled as Assertion $$\mathbf{A}$$ and the other is labelled as Reason $$\mathbf{R}$$.

Assertion A: Phenolphthalein is a $$\mathrm{pH}$$ dependent indicator, remains colourless in acidic solution and gives pink colour in basic medium.

Reason R: Phenolphthalein is a weak acid. It doesn't dissociate in basic medium.

In the light of the above statements, choose the most appropriate answer from the options given below.

Which technique among the following, is most appropriate in separation of a mixture of $$100 \,\mathrm{mg}$$ of $$p$$-nitrophenol and picric acid ?

In base vs. acid titration, at the end point methyl orange is present as