Question

Magnesium is burnt in air to form $A$ and $B$. When $B$ is hydrolysed, $C$ and $D$ are formed. $D$ is the reactant in the manufacture of nitric acid by Ostwald's process. What is $C$

• A. $\ce{NH_3}$
• B. $\ce{Mg(OH)_2}$
• C. $MgO$
• D. $NO$

Answer 1

Answer: (B)

When magnesium is burnt in air, it forms two products $(A$ and $B)$. The, compound '$A$' is magnesium oxide and compound ' $B$' is traces of magnesium nitride (formed as a result of reaction between magnesium and molecular nitrogen).

Now, on hydrolysis of magnesium nitride $(B)$, it forms ammonia and magnesium hydroxide.

Since, '$D$' is the reactant in the manufacture of nitric acid by Ostwald's process. Thus, compound '$D$' is $NH _{3}$ and compound ' $C$' is $Mg ( OH )_{2}$.

The respective reactions for the following information are as follows:

$2Mg(s) + O_2(g) \ce{->[\Delta]} \underset{'A'}{2MgO(s)}$ (magnesium oxide)

$3Mg(s) + N_2(g) \rightarrow \underset{'B'}{Mg_3N_2(s)}$ (magnesium nitride)

$Mg_3N_2(s) + 6H_2O(l) \rightarrow \underset{C}{3Mg(OH)_2(s) }+ 2NH_3(g)$ (magnesium hydroxide)