I believe the answer is A (it was on another Brainly question as well).
Answer:
Ammonia gas(an alkaline gas with characteristics of choking or irritating smell) is not liberated when 6mole of HCl is added to the solution instead of 6mole of NaOH, to test for the presence of ammonium ion in the solution
Explanation:
As expected, when testing for ammonium ion in a solution (precisely ammonium salt solution), Sodium Hydroxide (NaOH) is required as the test reagent.
When NaOH is added to the solution, A gas with characteristics of choking or irritating smell is liberated.
This gas turn red litmus paper blue.
This liberated gas is an alkaline gas, which is confirmed as an ammonia gas(NH3).
If HCl is added instead of NaOH, the ammonia gas will not be liberated, which indicates that the test reagent used is wrong.
