Question

For the following reaction, identify the substances being oxidized and reduced (including their oxidation numbers), the oxidizing agent and reducing agent.
SaCl4 + 2 Mg --> 2 MgCl2 + Si

Answer 1

Answer : 'Mg' being oxidized and reducing agent. 'Si' being reduced and oxidizing agent.

Explanation:

Oxidation reaction : It is defined as the reaction in which a substance looses its electrons. In this, oxidation state of an element increases. Or we can say that in oxidation, the loss of electrons takes place.

Reduction reaction : It is defined as the reaction in which a substance gains electrons. In this, oxidation state of an element decreases. Or we can say that in reduction, the gain of electrons takes place.

The balanced chemical reaction is :

$SiCl_4+2Mg\rightarrow 2MgCl_2+Si$

The half oxidation-reduction reactions are:

Oxidation reaction : $Mg\rightarrow Mg^{2+}+2e^-$

Reduction reaction : $Si^{4+}+4e^-\rightarrow Si$

From this we conclude that the 'Mg' is the reducing agent that loses electron to another chemical species in a redox chemical reaction and itself get oxidized due to increase in the oxidation number from (0) to (+2).

'Si' is the oxidizing agent that gains electron from another chemical species in a redox chemical reaction and itself get reduced due to decrease in the oxidation number from (+4) to (0).

Hence, 'Mg' being oxidized and reducing agent. 'Si' being reduced and oxidizing agent.

Answer 2

Chlorine, as a halogen, has oxidation number 1-, so in SiCl4, the charge of Si is 4+. This means that Si goes from 4+ to 0 charge, so it gains electrons and undergoes reduction. Meanwhile, Mg goes from 0 to 2+ charge, so it loses electrons and is oxidized. The oxidizing agent (which is the one reduced) is SiCl4, while the reducing agent (which is oxidized) is Mg.