Decolorization of KMnO₄ solution takes place when it reacts with ethene. The final product of  this reaction which is used as an anti-freeze is:

Ethylene glycol

The correct answer is option 1. Ethylene glycol.

The decolorization of potassium permanganate (KMnO₄) solution when it reacts with ethene (ethylene) results in the formation of ethylene glycol. KMnO₄ is a strong oxidizing agent and reacts with alkenes to form diols (compounds with two hydroxyl groups).

Here is the reaction:

In this reaction, ethene (CH₂=CH₂) reacts with KMnO₄ in the presence of water to form ethylene glycol (HOCH₂CH₂OH). Ethylene glycol is commonly used as an antifreeze in cooling and heating systems.

Therefore, the final product of this reaction, which is used as an antifreeze, is: Ethylene glycol.

Hydroxylation of ethene takes place in the presence of cold KMnO₄​ to form Ethylene glycol.