Question

One mole of magnesium nitride on the reaction with an excess of water gives:
A) One mole of ammonia.
B) One mole of nitric acid.
C) Two moles of ammonia.
D) Two moles of nitric acid.

Answer 1

Hint: The answer here is based on the general concept that deals with the reaction of nitrides with water that yield hydroxides and the release of ammonia gas and balancing this equation correctly leads you to the correct answer.

Complete step by step answer:
From the previous chapters of inorganic chemistry, we have studied about the nitrides which is having the general formula ${{N}_{3}}^{-}$
Let us now see what happens when the nitrides are reacted with water.
- Nitride is a compound of nitrogen in which the formal charge on nitrogen is -3 and this nitride ion is never encountered in the protic solutions because it is highly basic and can be protonated very easily.
- Now, the given question involves one mole of magnesium nitride wherein the molecular formula of magnesium nitride is $M{{g}_{3}}{{N}_{2}}$
This, when reacts with excess of water the reaction yields magnesium hydroxide along with the release of ammonia gas and thus the reaction is as shown below,
\[M{{g}_{3}}{{N}_{2}}+{{H}_{2}}O\to Mg{{(OH)}_{2}}+N{{H}_{3}}\]
- Since the above reaction is not balanced, the balancing of the reaction gives us total number of moles of ammonia released that is:
\[M{{g}_{3}}{{N}_{2}}+6{{H}_{2}}O\to 3Mg{{(OH)}_{2}}+2N{{H}_{3}}\]
Therefore, there is release of two moles of ammonia when one mole of magnesium nitride reacts with excess of water.
So, the correct answer is “Option C”.

Note: While solving these types of questions, balancing of chemical reaction is to be noted and the small change in this will lead to the wrong answers. Be thorough with the concept of balancing a chemical reaction.