Question

Which of the following is an intermolecular redox reaction?
A.\[2OCH-CHO\xrightarrow{O{{H}^{-}}}HOC{{H}_{2}}-C{{H}_{2}}OH\]
B.\[2{{C}_{6}}{{H}_{5}}CHO\xrightarrow{Al{{(O{{C}_{2}}{{H}_{5}})}_{3}}}{{C}_{6}}{{H}_{5}}COOH+{{C}_{6}}{{H}_{5}}C{{H}_{2}}OH\]
C.\[4Cr{{O}_{5}}+{{H}_{2}}S{{O}_{4}}\to 2C{{r}_{2}}{{(S{{O}_{4}})}_{3}}+{{H}_{2}}O+7{{O}_{2}}\]
D.\[A{{s}_{2}}{{S}_{3}}+HN{{O}_{3}}\to {{H}_{3}}As{{O}_{4}}+{{H}_{2}}S{{O}_{4}}+NO\]

Answer 1

Hint: Redox is a type of chemical reaction in which the oxidation states of atoms are changed. Redox reactions are characterized by the actual or formal transfer of electrons between chemical species, most often with one species undergoing oxidation while another species undergoes reduction. In an intermolecular redox reaction, oxidation-reduction takes place when molecules of two different substances react with each other.

Complete step by step answer:
The following reaction is a redox reaction as it is the reaction in which there is a change in oxidation state of the elements in the reactant side and the product side.
\[A{{s}_{2}}{{S}_{3}}+HN{{O}_{3}}\to {{H}_{3}}As{{O}_{4}}+{{H}_{2}}S{{O}_{4}}+NO\]
As in this reaction the Oxidation state of Sulphur in \[A{{s}_{2}}{{S}_{3}}\]​ is -2 whereas in sulphuric acid \[{{H}_{2}}S{{O}_{4}}\]​ it is +6, means it is oxidised.
And similarly we have a change in oxidation state of Nitrogen, Oxidation State of N in \[HN{{O}_{3}}\]​ is +5 whereas in NO it is +2 which means it is reduced during the redox reaction. So as one is reducing and other is oxidising agent hence this reaction is between two different compounds so it is an intermolecular redox reaction.
In any other option this thing does not occur so they cannot be called intermolecular redox reactions.
Hence, the correct answer is option D.

Note:
In any Intramolecular redox reaction, the molecule of a single substance undergoes oxidation-reaction by the process decomposition.
Oxidation number, also called oxidation state, the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.