Question

What happens when magnesium is burnt in air and the products X and Y is treated with water?
$Mg\xrightarrow{air}\begin{matrix} X \\\ {{\downarrow }^{{{H}_{2}}O}} \\\ P \\\ \end{matrix}+\begin{matrix} Y \\\ {{\downarrow }^{{{H}_{2}}O}} \\\ P+Q \\\ \end{matrix}$

| X| Y| P| Q
---|---|---|---|---
A| $MgO$ | $Mg{{(OH)}_{2}}$| $Mg{{(OH)}_{2}}$ | ${{N}_{2}}$
B| $MgO$| $M{{g}_{3}}{{N}_{2}}$ | $Mg{{(OH)}_{2}}$| $N{{H}_{3}}$
C| $MgO$| $M{{g}_{3}}{{N}_{2}}$| $Mg{{(OH)}_{2}}$| ${{N}_{2}}$
D| $MgO$| $MgC{{O}_{3}}$ | $Mg{{(OH)}_{2}}$| $C{{O}_{2}}$

Answer 1

To answer the given statement, you should properly know about the chemical reactions of the magnesium and about their reactants formed after the reaction and after that you can easily solve the given reactions accordingly and identify the correct option.

Complete answer:
Considering the statement as-
When magnesium is burnt in the air consisting of the oxygen and the nitrogen gas then, it results in the formation of the oxide and the nitride i.e. the magnesium oxide (X) and the magnesium nitride (Y).
The chemical reaction is supposed to take place as;
$5Mg+{{O}_{2}}+{{N}_{2}}\to 2MgO+M{{g}_{3}}{{N}_{2}}$
Now, when this magnesium oxide and the magnesium nitride so, formed is made to undergo reaction with the water, it results in the formation of the hydroxides i.e. magnesium hydroxide but magnesium nitride also produces ammonia along with the magnesium hydroxide.
The reaction is supposed to take place as;
$\begin{aligned} & MgO+{{H}_{2}}O\to Mg{{(OH)}_{2}} \\\ & M{{g}_{3}}{{N}_{2}}+{{H}_{2}}O\to 3Mg{{(OH)}_{2}}+2N{{H}_{3}} \\\ \end{aligned}$
So, thus when magnesium is burnt in air and the products magnesium oxide and magnesium nitride is treated with water , it results in the formation of the magnesium hydroxide along with the ammonia (in case of magnesium nitride).
The overall reaction is supposed to take place as;
$Mg\xrightarrow{air}\begin{matrix} MgO \\\ {{\downarrow }^{{{H}_{2}}O}} \\\ Mg{{(OH)}_{2}} \\\ \end{matrix}+\begin{matrix} M{{g}_{3}}{{N}_{2}} \\\ {{\downarrow }^{{{H}_{2}}O}} \\\ Mg{{(OH)}_{2}}+N{{H}_{3}} \\\ \end{matrix}$

Hence, option (b) is correct.

Note:
Don’t forget to balance the chemical reactions after writing them. And by balancing a chemical reaction, we simply mean that the no. of moles of each atom on the reactant side must be equal to the number of moles of each atom on the product side.