which of the following is an oxidation - reduction reaction?\no fe2o3 + 3co → 2fe + 3co2\no cuso4 + 2naoh →…

Explanation:

Step1: Recall redox - reaction criteria

A redox reaction has a change in oxidation numbers of elements.

Step2: Analyze the first reaction

In $\ce{Fe2O3 + 3CO\rightarrow2Fe + 3CO2}$, in $\ce{Fe2O3}$, the oxidation number of $\ce{Fe}$ is $+ 3$, and it changes to $0$ in $\ce{Fe}$. In $\ce{CO}$, the oxidation number of $\ce{C}$ is $+2$, and it changes to $+4$ in $\ce{CO2}$. So, this is a redox reaction.

Step3: Analyze the second reaction

In $\ce{CuSO4 + 2NaOH\rightarrow Cu(OH)2+Na2SO4}$, it is a double - displacement reaction. Oxidation numbers of $\ce{Cu}$, $\ce{S}$, $\ce{Na}$, $\ce{O}$, and $\ce{H}$ remain the same throughout the reaction.

Step4: Analyze the third reaction

In $\ce{2NaOH + H2CO3\rightarrow Na2CO3 + 2NaOH}$, it is an acid - base reaction. Oxidation numbers of elements do not change.

Step5: Analyze the fourth reaction

In $\ce{Pb(NO3)2+Na2SO4\rightarrow2NaNO3 + PbSO4}$, it is a double - displacement reaction. Oxidation numbers of $\ce{Pb}$, $\ce{N}$, $\ce{O}$, $\ce{Na}$, and $\ce{S}$ remain the same.

Answer:

$\ce{Fe2O3 + 3CO\rightarrow2Fe + 3CO2}$