OCR Chemistry F322~ 4th June 2013~ AS Chemistry

Original post by ellie2996

Completely confused myself :s-smilie:

is an exothermic reaction bond breaking or bond making???

An exothermic reaction is when the ethalpy of the products is less than that of the reactants and so energy is released. Bond breaking is endothermic and bond making is exothermic :smile:

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Reply 1281

OP

Could anyone help in the question attached?

I know that the formula of the isomers is C5H10, and I have found the E/Z isomerism structures of the F and G, but how do your work out the structure of H?

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Reply 1282

OP

ImageUploadedByStudent Room1370085247.981734.jpg139.7KB

Here's the actual question

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Reply 1283

yodawg321

12

Original post by Jimmy20002012

Could anyone help in the question attached?

I know that the formula of the isomers is C5H10, and I have found the E/Z isomerism structures of the F and G, but how do your work out the structure of H?

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Don't you attached all the groups on one carbon atom?

Reply 1284

Original post by Jimmy20002012

Could anyone help in the question attached?

I know that the formula of the isomers is C5H10, and I have found the E/Z isomerism structures of the F and G, but how do your work out the structure of H?

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I can't see the question but H will not have E/Z isomerism and as it is an unsymmetrical alkene the double bond must be on carbon-1.

Reply 1285

GeneralOJB

Anyone know where I can get practise questions? I've done all the papers for this spec like I presume most people have now. The old past papers were used by my college for tests and homeworks too.

Reply 1286

OP

Original post by JimmyA*

I can't see the question but H will not have E/Z isomerism and as it is an unsymmetrical alkene the double bond must be on carbon-1.

Don't still get it, how do you work it out? I attached the question above :smile:

Reply 1287

needtosucceed=)

10

Original post by ss2012

How do you know how many isomers C5H12 has?

just draw them all out :smile:

Reply 1288

Original post by Jimmy20002012

Don't still get it, how do you work it out? I attached the question above :smile:

The molecule is an alkene as it's formula fits the general formula CnH2n. That means its functional group is a C-C double bond. There is only 2 places this can go, on carbon-1 or carbon-2. On carbon-2 the E/Z isomer occurs. When on carbon-1 its just a structural isomer.

Reply 1289

That_Clever_Guy

2

Original post by Jimmy20002012

Could anyone help in the question attached?

I know that the formula of the isomers is C5H10, and I have found the E/Z isomerism structures of the F and G, but how do your work out the structure of H?

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Couldn't it be a straight chained alkene with the double bond attached between two other carbon atoms? For example you could have pent-2-ene or pent-3-ene :smile:

Sorry but i haven't seen the question

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Reply 1290

needtosucceed=)

10

Original post by GeneralOJB

Anyone know where I can get practise questions? I've done all the papers for this spec like I presume most people have now. The old past papers were used by my college for tests and homeworks too.

you probably haven't done all the old spec papers so go to

http://www.freeexampapers.com/

alevel>chemistry>ocr

or someone else suggested going to different exam boards as the stuffs similar :smile:

Reply 1291

OP

Original post by JimmyA*

The molecule is an alkene as it's formula fits the general formula CnH2n. That means its functional group is a C-C double bond. There is only 2 places this can go, on carbon-1 or carbon-2. On carbon-2 the E/Z isomer occurs. When on carbon-1 its just a structural isomer.

Okay, thanks :smile:

Reply 1292

needtosucceed=)

10

Original post by That_Clever_Guy

Couldn't it be a straight chained alkene with the double bond attached between two other carbon atoms? For example you could have pent-2-ene or pent-3-ene :smile:

Sorry but i haven't seen the question

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those would be the e/z isomers, not the structural ones :smile:

Reply 1293

OP

Original post by needtosucceed=)

those would be the e/z isomers, not the structural ones :smile:

Hey needtosucceed could you explain the question I posted above, to do with the E/Z isomerism and structural isomerism :smile:

Reply 1294

Original post by That_Clever_Guy

Couldn't it be a straight chained alkene with the double bond attached between two other carbon atoms? For example you could have pent-2-ene or pent-3-ene :smile:

Sorry but i haven't seen the question

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Pent-3-ene doesn't exist. Its would be pent-2-ene

Reply 1295

That_Clever_Guy

2

Original post by JimmyA*

Pent-3-ene doesn't exist. Its would be pent-2-ene

Of course yeh sorry :s

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Reply 1296

OP

Original post by JimmyA*

Pent-3-ene doesn't exist. Its would be pent-2-ene

With that question, say they gave you a 5-7 carbon chain, how would you then work out the isomer H, or would they allow multiple answers then?

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Reply 1297

Has a question on protocols ever actually come up? I can't remember doing a question on.

Reply 1298

Original post by Jimmy20002012

With that question, say they gave you a 5-7 carbon chain, how would you then work out the isomer H, or would they allow multiple answers then?

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You wouldn't get a question like it, but if they did they would allow multiple answers

Reply 1299

OP

Original post by JimmyA*

Has a question on protocols ever actually come up? I can't remember doing a question on.

Well it an actual question about them, but they have asked questions about how to reduce greenhouse emissions where one of the mark scheme answers are protocols such as the Montreal and Kyoto protocol has been developed which allow countries to work together in order to reduce greenhouse emissions. :smile: