What is cracking in crude oil processing and why is it used?

• A. Cracking removes impurities from crude oil.
• B. Cracking breaks long-chain hydrocarbons into shorter ones to produce more valuable fuels, typically using heat and/or a catalyst.
• C. Cracking adds hydrogen across double bonds.
• D. Cracking converts alkanes to alkenes only.

Answer: (B)

Cracking is a process that breaks long hydrocarbon chains into shorter ones. This matters because crude oil contains heavy molecules that are less useful as fuels, so turning them into smaller, more valuable fuels like petrol (gasoline) and diesel helps meet demand. The operation often uses heat (thermal cracking) or a catalyst (catalytic cracking) to break the carbon–carbon bonds more efficiently. Catalytic cracking, in particular, operates at lower temperatures and produces a mix that includes branched alkanes and aromatics, which are desirable components for fuels. The other descriptions don’t fit: cracking doesn’t remove impurities, it doesn’t involve adding hydrogen everywhere (that would be hydrogenation), and it isn’t limited to converting alkanes to alkenes only.