which of the following is an oxidation - reduction reaction?\nso₂(g) + h₂o(l) → h₂so₃(aq)\ncaco₃(s) → cao(s)…

Explanation:

Step1: Recall oxidation - reduction reaction concept

An oxidation - reduction reaction has a change in oxidation numbers of elements.

Step2: Analyze first reaction

For $SO_2(g)+H_2O(l)\rightarrow H_2SO_3(aq)$, the oxidation numbers of $S$, $O$ and $H$ do not change. S in $SO_2$ has an oxidation number of +4, in $H_2SO_3$ also +4; H is + 1 and O is -2 throughout.

Step3: Analyze second reaction

For $CaCO_3(s)\rightarrow CaO(s)+CO_2(g)$, the oxidation numbers of $Ca$, $C$ and $O$ remain the same. Ca is +2, C is +4 and O is -2 in both reactants and products.

Step4: Analyze third reaction

For $Ca(OH)_2(s)+H_2CO_3(l)\rightarrow CaCO_3(aq)+2H_2O(l)$, it is a double - displacement reaction and no change in oxidation numbers of elements.

Step5: Analyze fourth reaction

For $C_6H_{12}O_6(s)+6O_2(g)\rightarrow 6CO_2(g)+6H_2O(l)$, in $C_6H_{12}O_6$, the average oxidation number of C is 0. In $CO_2$, the oxidation number of C is +4. Also, the oxidation number of O changes from 0 in $O_2$ to -2 in $CO_2$ and $H_2O$. There is a change in oxidation numbers, so it is an oxidation - reduction reaction.

Answer:

$C_6H_{12}O_6(s)+6O_2(g)\rightarrow 6CO_2(g)+6H_2O(l)$