Question

A piece of magnesium ribbon is heated to redness in an atmosphere of nitrogen and on cooling water is added the gas evolved is:
(A) Ammonia
(B) Hydrogen
(C) Nitrogen
(D) Oxygen

Answer 1

Magnesium reacts with nitrogen to form magnesium nitride, $M{g_3}{N_2}$ as a greenish yellow amorphous powder. On reaction with water Magnesium will form magnesium hydroxide $Mg{(OH)_2}$ and ammonia $N{H_3}$.

Complete Solution :
So, let us see the reactions taking place.
-We know that Magnesium ribbon is silver in colour. When a piece of magnesium ribbon is heated to redness in the atmosphere in presence of nitrogen, the following reaction takes place
$3Mg + {N_2}\xrightarrow{{Burning}}M{g_3}{N_2}$

-The ribbon burns with a bright white light. We can also see that a very intense heat is being produced in this reaction. Burning of Magnesium will cause it to react with the oxygen that is present in the atmosphere. This will produce a powdery ash called Magnesium oxide.
-But here the reaction is just focused on with nitrogen. So, that reaction is only desired.
-Now, the magnesium nitrate undergoes hydrolysis and forms ammonia gas as follows:
$M{g_3}{N_2} + 6{H_2}O \to 3Mg{(OH)_2} + 2N{H_3} \uparrow$

Clearly, the gas formed is ammonia.
So, the correct answer is “Option A”.

Note: - The ammonia gas can be found out by a characteristic pungent smell.
- Ammonia is a biological agent in organisms which helps to form amino acids.
- Ammonia forms amino acid which is the basic building blocks of proteins. It is also widely used for cleaning water, etc.