ANS:A - Coking tendency increases with increasing molecular weight.

The correct statement among the options provided is: Coking tendency increases with increasing molecular weight. Here's why:

• Coking Tendency and Molecular Weight: Coking refers to the formation of carbonaceous deposits (coke) on catalyst surfaces or in process equipment during refining processes. Higher molecular weight hydrocarbons have more complex structures and tend to decompose less readily than lighter hydrocarbons. As a result, heavier molecules are more likely to undergo reactions leading to coke formation under certain conditions, such as high temperatures or insufficient hydrogen availability.
• Higher Pressure and Coke Formation: Higher pressure generally does not enhance coke formation directly. Instead, coke formation is influenced more significantly by factors such as temperature, residence time, catalyst activity, and hydrogen availability.
• Coking as an Exothermic Reaction: Coking is typically considered an endothermic reaction because it involves the breaking of carbon-carbon bonds in hydrocarbons, which requires energy input (heat). The deposition of carbonaceous materials (coke) is generally seen as an accumulation of byproducts rather than a heat-releasing process.