The question asks to identify why the given reaction is classified as an oxidation reaction based on the classical (oxygen-based) concept. We need to recall the definition of oxidation in terms of oxygen transfer.
A) Gains oxygen — In the reaction \(2\text{Mg(s)} + \text{O}_2\text{(g)} \rightarrow 2\text{MgO(s)}\), magnesium (\(\text{Mg}\)) combines with oxygen (\(\text{O}_2\)) to form magnesium oxide (\(\text{MgO}\)). This clearly shows that magnesium has gained oxygen, which is the classical definition of oxidation.
The question asks about the classical understanding of reduction, specifically in the context of converting metal oxides to free metals. We need to identify which option correctly describes this historical definition.
Correct Option: A) The reduction of metal oxides (e.g., of copper or lead) to the metal by heating with carbon or hydrogen. This option perfectly describes the classical understanding of reduction as the removal of oxygen from a compound, specifically converting metal oxides into their elemental metal form.
The question asks to identify the substance that is reduced in the given chemical reaction based on the classical concept of reduction. The classical concept defines reduction as the gain of hydrogen or the loss of oxygen, and oxidation as the loss of hydrogen or the gain of oxygen.
B) Copper oxide (CuO), since it loses oxygen to form copper metal
This statement correctly identifies \(\text{CuO}\) as the substance reduced because it loses oxygen, which aligns with the classical definition of reduction.
The question asks to identify the chemical process when hydrogen is removed from a compound, according to the classical definition of chemical reactions. We need to recall the classical definitions of oxidation and reduction.
A) Oxidation — As per the classical definition, the removal of hydrogen from a compound is considered oxidation. This process is also known as dehydrogenation.
The question asks about the limitations of the classical definition of oxidation and reduction, which is based on the transfer of oxygen or hydrogen. We need to identify why this classical definition was found to be insufficient.
\[ 2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl} \]
In this reaction, sodium is oxidized (loses electrons) and chlorine is reduced (gains electrons), but there is no oxygen added or hydrogen removed/added. The classical definition fails to explain such reactions.
Correct Option: D) Could not explain redox changes that do not involve oxygen or hydrogen at all, such as reactions between chlorine and metals
The question asks for the modern definition of oxidation based on electron transfer. We need to recall the definitions of oxidation and reduction in terms of electron gain or loss.
Correct Option: B) A net loss of one or more electrons by a species