In which of the following reactions, $\mathrm{MgO}$ is not formed?

In which of the following reactions, $\mathrm{MgO}$ is not formed?
  1. $\mathrm{Mg}+\mathrm{CO}_2 \longrightarrow$
  2. $\mathrm{Mg}+$ dil. $\mathrm{HNO}_3 \longrightarrow$
  3. $\mathrm{Mg}+\mathrm{NO} \stackrel{\Delta}{\longrightarrow}$
  4. $\mathrm{Mg}+\mathrm{B}_2 \mathrm{O}_3 \longrightarrow$

Solution

$\begin{aligned} & \mathrm{Mg}+2 \mathrm{HNO}_3 \rightarrow \mathrm{Mg}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \uparrow \\ & \text { dil. } \\ & \end{aligned}$ Hence, $\mathrm{MgO}$ is not formed in this reaction.

Asked in: AP EAMCET 2005

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