Question

How can you distinguish between $diluteHCl$ and $diluteHN{O}_3$?

• A. By adding a few drops of silver nitrate
• B. By adding a few drops of sodium hydroxide
• C. By adding a few drops of red litmus
• D. By adding a few drops of phenolphthalein

Answer 1

The correct option is A

By adding a few drops of silver nitrate

This is a great opportunity to use the silver nitrate test. By adding, a few drops of $AgN{O}_3$ to dilute HCl, we get a white precipitate of silver chloride.

$HCl+AgN{O}_3\to AgCl\downarrow +HN{O}_3$

On the other hand, there is no reaction when a dilute solution of nitric acid is treated with silver nitrate solution.

Phenolphthalein would remain colourless in both the solutions and litmus solution would turn red in both the solutions as both are strong acids

if both are treated with sodium hydroxide, they would undergo acid-base neutralisation. Hence this cannot be sued to distinguish the two acids.