Which of the following is an oxidation-reduction reaction?
so2(g) + h2o(l) h2so3(aq)
caco3(s) cao(s) + co2(g)
ca(oh)2(s) + h2co3(l) caco3(aq) + 2h2o(l)
c6h12o6(s) + 6o2(g) 6co2(g) + 6h2o(l)

Explanation: Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.

Oxidation reaction is defined as the reaction in which a substance looses its electrons. Reduction reaction is defined as the reaction in which a substance gains electrons.

For the given options:

Option A:

This is a combination reaction because two compounds are reacting to form a single compound.

Option B:

The above reaction is decomposition reaction because a single compound is breaking down into two compounds.

Option C:

The above reaction is a neutralization reaction because an acid reacts with base to produce salt and water.

Option D:

The oxidation state of oxygen changes from 0 to -2, it is gaining electrons. Thus, it is getting reduced and it undergoes reduction reaction. The carbon is getting oxidized and thus it undergoes oxidation reaction.

Thus, it is considered as redox reaction.

Hence, the correct answer is Option D.

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

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