Products of catalytic cracking (2 Viewers)

[itacr7]

Is ethylene always one of the products formed from Catalytic cracking? If not then how do I determine the products?

 

[faisalabdul16]

Is ethylene always one of the products formed from Catalytic cracking? If not then how do I determine the products?

Products formed are ethylene and an alkane.

 

[SuchSmallHands]

Is ethylene always one of the products formed from Catalytic cracking? If not then how do I determine the products?

No, it's not always ethylene which forms. What you get from cracking a longer hydrocarbon chain is a smaller alkene (any smaller alkene, not necessarily ethylene - though propene and ethylene will be the two greatest constituents of the mixture) and alkane. That's why we distil the products of cracking, to isolate the ethylene.

As for how you determine the products, we can't exactly do that. The hydrocarbon you're cracking will definitely become an alkane and alkene, the exact alkane and alkene you will end up with can't be determined though. It's like taking a stick and snapping it in half, before you do it there's no way to work out the exact size of the two pieces you'll end up with.

 

[Kaido]

It's like taking a stick and snapping it in half.

Guys, do not try this at home.

 

[itacr7]

Ok so let's say there is a question asking to show the catalyctic cracking of a long chainedhydrocarbon such as decane would the safest option be assuming it's either ethene or propene?

 

[SuchSmallHands]

Ok so let's say there is a question asking to show the catalyctic cracking of a long chainedhydrocarbon such as decane would the safest option be assuming it's either ethene or propene?

They can't mark you wrong for writing any smaller alkene and alkane, but since ethylene is course relevant yeah, you'd be better off writing that. Remember that if you're cracking decane and one of the products is ethylene the other will have to be octane to make sure you end up with the same number of carbon atoms you started with.

 

[elkedag]

The products should just be some number of alkanes/alkenes/H2 which balance the equation. The question will sometimes give you one of the products.

 

[Kaido]

HSC questions won't be ambiguous and if it is so, it's likely a MC with an obvious answer.

 

[happypeople]

No, ethylene will not always be a product of catalytic cracking.

Although catalytic cracking does definitely produce smaller alkanes/alkenes (which don't have to be ethylene).

In the HSC, they will either specify which products they want you to write in the equation (such as multiple choice questions and short answers), or they will ask you to determine which equation is correct in terms of balancing of reactants and/or the production of smaller alkanes/alkenes (common for MCQ) (there may be other types of questions, but these two are the most common that I've come across when completing past HSC Chemistry papers).

Hope this helps! Good luck with your studies!