Cracking

[destain]

Can someone explain cracking please

and 2 chemical equations in which ethene acts as a reactant..

[charmanderp]

Thermal cracking is when you apply heat and pressure to an alkane to produce smaller molecules, usually a smaller alkane and an alkene. This is useful because alkenes are more reactive, and are hence more productive for us in the industrial process. For example, propane can be cracked to give ethene and methane. There is also catalytic cracking, but you don't need to know about that.

The two types of reactions which involve ethene (or alkenes in general) are addition reactions and polymerisation. In addition reactions we pass a chemical across the ethene molecule to break the double bond and saturate the molecule, that is give it the maximum number of substituents. Examples include hydrogenation (adding hydrogen), hydration (adding water) and halogenation (adding a halogen). Addition polymerisation is when we take an unsaturated molecule and amplify it to get a chain of the molecule with repeating patterns.

[destain]

oh so some form of organic chem thanks i didnt know haha..

and.......
which one of the following is LEAST likely to be a product of a redox reaction between sulfuric acid and zinc metal?
a) H2
b) H2S
c) SO2
d) SO3

and why please

[charmanderp]

Calculated which product doesn't produce a different oxidation number for sulfur.

Hint: It's D.

[destain]

LOL thanks

and...
Which of the followings statements would apply to compounds that belong to the same homologous series?

I got the answer but it adds this statement: They contain the same functional group

I thought if you're in the same homologous series, it just means you differ by a CH2, doesn't mean you have to have the same functional group or something...kinda confused

[charmanderp]

How could they 'just differ by a CH2' if they didn't have the same functional groups? In that case they'd differ by more than just a CH2 group, and wouldn't really be homo(meaning the same)logous anymore.

And they don't specifically differ by just a CH2. For example methane and decane differ by a lot more.

[destain]

i think i was reading the question wrongly as in, if you have the same functional group it means you're in the same homologous series
instead of to be IN the same homologous seriesi you need the same functional group? LOL

[charmanderp]

Either way, molecules MUST have share an identical number and selection of functional groups to be in the same homologous series. Unless of course there are no functional groups, such as in halides and alkanes.

[destain]

Can you crack C3H8 into C2H6? and CH2 is incorrect yes?

Just by the way, what chapter is cracking in, in unit 3

and I thought C2H6 was an answer as it is a smaller alkane?

[charmanderp]

CH2 can't exist on its own, hence  propene can only be cracked into ethene and methane.

[pi]

Just by the way, what chapter is cracking in, in unit 3

It isn't really mentioned in the book

[jadams]

Just by the way, what chapter is cracking in, in unit 3

It isn't really mentioned in the book

Is it technically part of the course?

[pi]

Just by the way, what chapter is cracking in, in unit 3

It isn't really mentioned in the book

Is it technically part of the course?

It's worth knowing (it isn't particularly difficult), but I think I only saw it on one trial exam. Not sure if it's specifically on the course though.

[charmanderp]

You just have to know that it's an option and what exactly it does.

[pi]

Just had a quick look at the study design, it isn't mentioned.