Question

Take a long magnesium ribbon. Heat it over a flame when it burns with a bright light and is converted into a white powder $\mathrm{MgO}$. It is called a -

• A. combination reaction
• B. displacement reaction
• C. decomposition reaction
• D. thermal reaction

Answer 1

The correct option is A

combination reaction

Explanation of the correct option:

The correct option is A:

• It is called the combination reaction because when the Magnesium ribbon$\left(Mg\right)$ is burned it combines with Oxygen$\left(O_2\right)$ available in the air to form the Magnesium oxide$\left(MgO\right)$. The following reaction represents this phenomenon.
• $\underset{\left(\mathrm{Magnesium}\right)}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\left(\mathrm{Magnesium}\mathrm{oxide}\right)}{2\mathrm{MgO}\left(\mathrm{s}\right)}$
• In the combination reaction, the resultant compound is formed by the combination of two or more compounds.

Explanation of the incorrect options:

• Option B: In the reaction $\underset{\left(\mathrm{Magnesium}\right)}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\left(\mathrm{Magnesium}\mathrm{oxide}\right)}{2\mathrm{MgO}\left(\mathrm{s}\right)}$, no element is displaced to form the Magnesium oxide. So, it is not a displacement reaction.
• Option C: The Magnesium oxide is not formed by breaking down a compound. Instead, it is formed by combining the compounds.
• Option D: The thermal reaction generally performs the decomposition of substance to form the new compound but in the reaction, no decomposition is performed.

Final Answer: The reaction $\underset{\left(\mathrm{Magnesium}\right)}{2\mathrm{Mg}\left(\mathrm{s}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\left(\mathrm{Magnesium}\mathrm{oxide}\right)}{2\mathrm{MgO}\left(\mathrm{s}\right)}$ can be called the combination reaction.