Question

When burning magnesium ribbon is introduced into a jar of oxygen, it produces:
(A).Mg
(B).MgO
(C).${ Mg }_{ 2 }{ O }$
(D).${ Mg }_{ 2 }{ { O }_{ 2 } }$

Answer 1

Compounds formed after combination of two or more elements depend on the valence number of the particular element. Magnesium is having valence number 2 , similarly Oxygen is also having a valence number of 2, from this it is easy to find the product formed.

Complete step by step solution:
Magnesium ribbon, introduced into a jar of oxygen will produce Magnesium Oxide (MgO).
The reaction takes place according to the given chemical equation:
${ 2Mg\quad + }\quad { O }_{ 2 }\quad \rightarrow \quad { 2MgO }$
When magnesium is in its metal form it will burn very easily in air. However, in order to start the reaction (the burning) the magnesium metal needs a source of energy.
The flame provides a source of heat so that the magnesium metal atoms can overcome their activation energy.
Activation energy is the minimum energy required in order for a chemical reaction to proceed.
Magnesium gives up two electrons to oxygen atoms to form this powdery product.
This is an exothermic reaction. An exothermic reaction is a term that describes a chemical reaction in which there is a net release of energy.
Now let us look at why other options are incorrect.
Option (A) Mg is not the correct option, since, in the question it is mentioned that a ‘burning’ Magnesium ribbon has been introduced into the oxygen jar. Since the activation energy (heat) has been already provided Mg will react with oxygen and will give MgO and will not exist as Mg only.
Option (B) MgO is the correct answer , as we have already explained above.
Option (C) ${ Mg }_{ 2 }{ O }$ is a wrong option. Because, oxygen is having a valence number of 2 and Magnesium is also having the valence number of 2, and in this scenario Mg2O cannot be formed, or rather let us say that such a compound doesn’t exist.
Option (D) ${ Mg }_{ 2 }{ { O }_{ 2 } }$ is a wrong option. It’s explanation is also similar to the above option (MgO).
The correct answer is Option (B) MgO.

Note: The burning magnesium ribbon produces light of sufficient intensity to cause temporary loss of sight. Avoid looking directly at the light source. The burning of magnesium in air produces intense heat which can cause burns and initiate combustion in flammable materials. Since a carbon dioxide fire extinguisher will not extinguish burning magnesium, a dry-powder extinguisher must be used.