Question

One mole of magnesium nitride on reaction with excess of water gives:
(a) One mole of nitric acid
(b) One mole of ammonia
(c) Two moles of ammonia
(d) Two moles of nitric acid

Answer 1

Hint: Magnesium nitride being readily soluble in water undergoes decomposition reaction in it. Decomposition reactions are those in which a single chemical compound splits into two or more chemical compounds. Solve the reaction.

Complete answer:
Magnesium nitride is a greenish yellowish inorganic compound made up of magnesium (Mg) and nitrogen (${{N}_ {2}} $) and its chemical formula is ${M{g}_ {3}} {{N}_ {2}} $.
In magnesium nitride, magnesium carries positive charge and nitrogen by gaining three electrons forms the nitride ion which carries the negative charge ($M{{g}^ {+3}} {{N}^ {-2}} $).
Magnesium nitride readily dissolves in water and has, thus, greater solubility in water than other organic solvents like methanol, ethanol etc. and undergoes decomposition reaction with water. It is so called a decomposition reaction because in this the magnesium nitride splits into the two chemical compounds, namely, magnesium hydroxide and ammonia.
Magnesium nitride on reaction with excess water splits into chemical compounds resulting in the formation of ammonia and magnesium hydroxide. The reaction proceeds as follows: -
         $M{{g}_ {3}} {{N}_ {2}} +{{H}_ {2}} O\to Mg{{(OH)} _ {2}} +N{{H}_ {3}}$
Now, balancing the number of moles of each reactant involving in reaction on both the sides, we get: -
      $M{{g}_ {3}} {{N}_ {2}} +6{{H}_ {2}} O\to 3Mg{{(OH)} _ {2}} +2N{{H}_ {3}} $
Thus, one mole of magnesium nitride on reaction with an excess of water gives two moles of ammonia.

Note:
Balance the equation properly. While balancing the equation the moles of each reactant, involved in the reaction, on reactant side and product side must be equal.