AS Mod 3 AQA - Cracking Watch

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Dipz
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#1
Report Thread starter 13 years ago
#1
Can someone help me with Cracking i dnt get :s thanks
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violet
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#2
Report 13 years ago
#2
splitting long chain alkanes into shorter chain alkanes and alkenes and hydrogen..

eg C14H30 ---> C7H16 + C3H6 + 2C2H4

basically, the shorter chains are more useful so the C-C and C-H bonds are broken to produce smaller alkanes

and i dunno what you need to know cos im not your board but the bonds are strong so the process has a high activation energy. therefore the precess needs a temp of ~450 degrees and a catalyst!
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Twiglet
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Report 13 years ago
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2 types of cracking: Thermal and Catalytic, they both have the same principal - to break long chain alkanes that are high in supply but low in demand, into shorter chain alkanes and alkenes which are in low supply but high demand...

Thermal Cracking
High temperature of 600 degrees
High pressure
Mechanism: free radical
High yield alkenes

Catalytic cracking
Zeolite catalyst
High temperature of 450 degrees
Slight pressure
Mechanism: ionic (involves carbocations0
High yield alkanes and aromatic hydrocarbons

Thats just a quick summary, I hope it helped a little (Im doing aqa aswell). Which particular bit is it that you dont understand?

franks x
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Kiesha
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Report 13 years ago
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And catalytic produces a higher yield of highly branched alkanes too.

But apart from that, that's all we need I think.
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Dipz
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#5
Report Thread starter 13 years ago
#5
ok thanks everyone really helped im finding module 3 hard
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