Q. Which of the following reactions does not involve oxidation-reduction?

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$2Rb+H_{2}O \rightarrow 2RbOH+H_{2}$

$2CuI_{2} \rightarrow 2CuI+I_{2}$

$CuO+H_{2} \rightarrow Cu+H_{2}O$

$4KCN+Fe\left(\right.CN\left(\left.\right)_{2} \rightarrow K_{4}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left]\right.$

Solution:

There is no change in the oxidation number of any species in the reaction so neither oxidation nor reduction occurs here.
$4KCN+Fe\left(\right.CN\left(\left.\right)_{2} \rightarrow K_{4}\left[\right.Fe\left(\right.CN\left(\left.\right)_{6}\left]\right.$

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