Question

The fast reaction between water and sodium is an example of:
A.Oxidation
B.Reduction
C.Intermolecular redox
D.Intramolecular redox

Answer 1

Hint: Redox reactions are of various types. This includes combination reactions, decomposition reaction, displacement reaction.Oxidation-reduction reactions are known as redox reaction. Here the oxidation state of one species will be increased and another will be decreased.

Complete step by step answer:
An increase in the oxidation of an element in a substance is called oxidation.
A decrease in the oxidation number of the element in the given substance is called reduction.
 A reagent which can increase the oxidation number of the element in a given substance is known as oxidants.
A reagent which can decrease the oxidation number of an element in a substance is known as reductant.
 Redox reactions are the combination of both of these reactions. That is a redox reaction is one in which both oxidation and reduction occur.
Intermolecular redox reactions are those in which redox reactions occur when two different molecules react.
Intramolecular redox reactions are those in which redox reactions occur within a single molecule. That is, intramolecular redox reaction occurs by the decomposition of a substance.
The reaction between water and sodium is given:
 \[2Na + 2{H_2}O \to 2NaOH + {H_2}\]
From this equation we can say that this is a redox reaction. Here redox reaction is intermolecular, because two molecules are reacting together. Initially the oxidation state of sodium was 0. After the reaction its oxidation state increases to +1. So, sodium undergoes oxidation. Similarly, initially the oxidation state of H was +1. After the reaction it has been decreased to 0. So, we can say that reduction occurs. Both oxidation and reduction has occurred.
Hence, the correct answer is C. The fast reaction between water and sodium is an intermolecular redox reaction.

Note: The redox reactions find applications in the study of electrode processes and cells. These are used in metallurgical processes. Metal oxides are reduced to metals by using suitable reducing agents. Redox reaction occurs in photosynthesis also. In photosynthesis, \[C{O_2}\] is reduced to carbohydrate and water is oxidised to oxygen.