What is the role of a catalyst in cracking and name a common type of catalyst?

• A. The catalyst lowers activation energy and promotes scission of long chains; zeolites.
• B. The catalyst adds long chains.
• C. The catalyst prevents cracking.
• D. The catalyst uses oxygen to oxidize.

Answer: (A)

Cracking works best when a catalyst provides an easier route for breaking long hydrocarbon chains into shorter ones. The catalyst lowers the activation energy of the C–C bond fission, so the reaction runs more readily at a given temperature. A common type of catalyst used in this process is zeolites, which are solid acidic materials with a porous structure. Their acidic sites catalyze the breaking of carbon–carbon bonds and help steer the product distribution toward desirable fuels. The other ideas—adding chains, preventing cracking, or using oxygen to oxidize—do not describe what happens in cracking, which is about breaking bonds, not building chains, stopping the reaction, or oxidizing substances.