Define olfactory indicator. Write the use of onion extract to distinguish between sodium hydroxide solutions and dilute hydrochloric acid.

The $\mathrm{pH}$ of solution $\mathrm{P}$ and $\mathrm{Q}$ are $3$ and $8$ respectively. Answer about the acidic and basic nature of $\mathrm{P}$ and $\mathrm{Q}$. In which solution is the concentration of ${\mathrm{H}}^{+}$ ions high?

The $\mathrm{pH}$ of solution $\mathrm{P}$ and $\mathrm{Q}$ are $3$ and $8$ respectively. Answer about the acidic and basic nature of $\mathrm{P}$ and $\mathrm{Q}$. Which solution would give red colour with universal indicator?

The $\mathrm{pH}$ of solution $\mathrm{P}$ and $\mathrm{Q}$ are $3$ and $8$ respectively. Answer about the acidic and basic nature of $\mathrm{P}$ and $\mathrm{Q}$. Which solution will give pink colour with phenolphthalein?