Question

A compound X is made to react with concentrated hydrochloric acid. The product formed by this reaction is Y. The compound Y is made to react with Z which results in the production of a brown precipitate. Identify X, Y and Z.

• A. i) Brown fumes ii) Dirty brown ppt is formed.
• B. i) Dirty brown ppt ii) Brown fumes is formed.
• C. Both i) and ii) give brown ppt.
• D. Both i) and ii) form brown fumes.

Answer 1

The correct option is A

i) Brown fumes

ii) Dirty brown ppt is formed.

Let us check the options and find out which one will satisfy all the conditions.

(1) X= Hydrochloric acid, Y= Sodium chloride, Z=Barium chloride

Hydrochloric acid will not react with hydrochloric acid to produce Potassium chloride so the first condition itself is not met. So this is not the answer.

(2) X= Sodium, Y=Sodium sulphate, Z= Sulphuric acid

Sodium reacts with HCl to produce Sodium chloride and not sodium sulphate so this is also not the answer.

(3) X= Calcium, Y=Calcium chloride, Z=Silver nitrate

Calcium reacts with HCl to produce calcium chloride so the first condition is met. When calcium chloride reacts with silver nitrate then a curdy white precipitate is formed rather than a brown precipitate. So this is also not the answer.

(4) X= Ammonia, Y=Ammonium chloride, Z= Nessler's reagent

Ammonia reacts with HCl to form ammonium chloride so the first condition is met. When ammonium chloride reacts with Nessler's reagent a brown precipitate is formed. So the second condition is also meet. Therefore this is the answer.

Note: Sometimes it helps to approach a question via options.