catalytic cracking (1 Viewer)

[bboyelement]

a question in our half yearlies ask what is the products when we crack ethane

i originally had this question right but our teacher was persuaded by one of the student, now i have it wrong so i want to make sure ... and also an included explanation is helpful thanks

 

[Riviet]

What was your answer and that other student's answer?

 

[bboyelement]

it was multiple choice ... i got down methane ... but now its ethene and hydrogen . but i thought methane was the best answer ...

 

[.ben]

I always thought it was only possilbe to crack larger hydrocarbons?!?!??!?!??!

 

[pkc]

Conversion of ethane to ethylene and hydrogen is called "Steam cracking"
Your teacher is correct. Although the name is misleading because there is no smaller hydrocarbons produced.

"Catalytic cracking" is the splitting of large molecules (eg naptha) into smaller molecules (eg ethene).

 

[Riviet]

Ah, I was right in thinking it had something to do with the steam cracking, that explains things.

 

[bboyelement]

uhm ... thanks a lot guys, i didnt think it would be steam cracking but i think the temperature gave it away, the question was : what do you get when you crack ethane at 850 degrees?

 

[funking_you]

a question in our half yearlies ask what is the products when we crack ethane

i originally had this question right but our teacher was persuaded by one of the student, now i have it wrong so i want to make sure ... and also an included explanation is helpful thanks

Your teacher is an idiot.

He/She should not put questions in an exam when they themselves do not know the actual answer.
It is stupid to expect a student to know the answer when the teacher does not know the answer.

YOU CAN crack ethane. There is not definate chemical equation you can write out which will give you the exact products that are always formed, this is because cracking proceeds by radicals, and radicals will form and combine with different species at different conditions.
HOWEVER,
realistically cracking ethane will produce BOTH methane and ethene and off the top of my head i can not say with confidence that it will form hydrogen gas, cause i dont think it will do that.

A simple reaction of cracking ethane would be:

2CH₃CH₃ ----> 2CH₄ + CH₂=CH₂


You said you teacher said that cracking ethane will produce just ethene and hydrogen gas, this is FALSE. This is not cracking, this is de-hydrogenation.


Hope that helps, and please pass this on to your teacher, if he/she doesnt agree with you, just send me a msg.

Cheers,
george

 

[adgala]

A simple reaction of cracking ethane would be:

2CH₃CH₃ ----> 2CH₄ + CH₂=CH₂

yeah i thought that catalytic cracking would mean that an alkane would turn into a smaller alkane and an alkene and not create hydrogen