Biology, Chemistry and Physics. Help

[Jono]

I got a chemistry question for any of you who does chemistry as a subject. Ive tried checkin up on google, but no luck.

Anyways the question is; Why is it important to exclude air in catalytic and thermal cracking?

I have an idea, but i am not sure.

[Sander]

i have chemistry but i think you are further than me, because i really dont understand

[TheGodEmperor]

i have chemistry but i think you are further than me, because i really dont understand

lol I hate all science...I knew some of this stuff, but even writing an answer would be pain. I am dropping it as soon as possible and taking English a year ahead  :thumbsup:

[a;sdlfkjas;df]

Anyways the question is; Why is it important to exclude air in catalytic and thermal cracking?

To avoid undesirable chemical reactions

I don't know how in depth you have to go, but that's where I'd start.

[Jono]

Can you go abit further into depth with it, imagine it is worth around 3-4 marks

[a;sdlfkjas;df]

I don't know really know what you're expected to know, but

You want alkenes.  In cracking hydrocarbons, you break down alkanes (no c-c multiple bonds, more stable) to get alkenes (c-c multiple bonds, less stable).  Without air, you avoid things like combustion which yields CH4 + 2O2 = 2H2O + CO2 (useless).

[Jono]

ahh yeah i get it, bease alkanes react with air to form carbon dioxide and water, therefor you wouldnt be getting the alkenes you want....

thanks heaps  :thumbsup:

[a;sdlfkjas;df]

Well not just that, but other things.  Basically, things in air react to form other things that you don't want (is what I'd put).

http://en.wikipedia.org/wiki/Pyrolysis

That's very similar to cracking.  You should be able to find things that would relate to air in cracking.

[Jono]

thanks heaps a;sdlfkjas;df  :thumbsup:

[Jono]

Hey how do i work o ut the number of monomers in a polymer?

The actual question is:

A sample of PVC has an average molecular wieght of 7.2 x 10^4; what is the average number of monomer units in a molecule of this sample?

I dont get it, please explain.

[a;sdlfkjas;df]

Start here:  http://en.wikipedia.org/wiki/Vinyl_chloride .  Pay attention to g/mol.

[Jono]

I cant find my answer anywhere, it doesnt talk about how to work out the number of monomers in a polymer etc, unless i read over it somewhere