Please let me know the answer of question no.11.

Dear student,
Answer to question 11 is given below:
HCl gas gives thick white fumes of ammonium chloride when glass rod dipped in ammonia solution is held near the vapors of the acid. NH₃ + HCl ⟶ NH₄Cl
With silver nitrate HCl gives white precipitate of silver chloride. The precipitate is insoluble in nitric acid but soluble in ammonium hydroxide. AgNO₃ + HCl ⟶ AgCl + HNO₃
A greenish yellow gas is liberated when concentrated hydrochloric acid is heated with oxidizing agent like manganese dioxide.
MnO₂+ 4HCl ⟶ MnCl₂ + 2H₂O + Cl₂
Regards