General thoughts: HSC chemistry 2015 (1 Viewer)

[Fizzy_Cyst]

Can somebody confirm this? I personally do not think it is D because despite the hydroxyl groups reacting in the middle correctly, if you have 2 of these units placed side by side, you would have a C - O - O - C bond which should't be so right?

I picked B because of this.

This is the condensation polymerisation of 1,4 butanedioic acid and ethylene glycol.

First step produces (B) which is ethylene glycol succinate (not a polymer), this then forms polyethylene glycol succinate (PES) which IS NOT (D), rather it is D without one of the 'O' atoms on either the LHS or RHS.

I maybe wrong, but I don't see there being a clear answer :\

Personally, I am thinking B is more correct as water is eliminated during this process and it involves two monomers joining :\

 

[JAMLO]

it is B also since the question states with these monomers and the rest all have n so by elimination its B

 

[monopoly73]

wtf ur not allowed to teach if you have impact on the tests conflict of interest reporting ur teacher to bostes

shes not a marker, she's a head marker meaning that she just overveiws everyone else marking so that they are consistent. and im pretty sure you can be a hsc marker and still teach cause my english and textile teachers are bother hsc markers

 

[IamKirby]

it is B also since the question states with these monomers and the rest all have n so by elimination its B

B is not a polymer in my opinion, but D is wrong also so not sure on this.

 

[Librah]

This is the condensation polymerisation of 1,4 butanedioic acid and ethylene glycol.

First step produces (B) which is ethylene glycol succinate (not a polymer), this then forms polyethylene glycol succinate (PES) which IS NOT (D), rather it is D without one of the 'O' atoms on either the LHS or RHS.

I maybe wrong, but I don't see there being a clear answer :\

Personally, I am thinking B is more correct as water is eliminated during this process and it involves two monomers joining :\

I think polymers need to have repeated sub-units by definition, might have to have this checked though.

 

[Librah]

It's very possible HSC have dungoofed, it has happened before.

 

[Ekman]

I think polymers need to have repeated sub-units by definition, might have to have this checked though.

This is what I thought, hence I picked D. I didn't pay attention to the extra oxygen at the end since it had the n brackets, and hence it is in polymer form

 

[Mr_Kap]

This is the condensation polymerisation of 1,4 butanedioic acid and ethylene glycol.

First step produces (B) which is ethylene glycol succinate (not a polymer), this then forms polyethylene glycol succinate (PES) which IS NOT (D), rather it is D without one of the 'O' atoms on either the LHS or RHS.

I maybe wrong, but I don't see there being a clear answer :\

Personally, I am thinking B is more correct as water is eliminated during this process and it involves two monomers joining :\

yeh i drew it myself to figure it out and saw that none of the answers were legit (i ended up going with D because it seemed like it was what they wanted.
I just wanted to add another option "E" and draw it correctly and pick that instead.

 

[invisible036]

Do you guys think they will give marks for crossed out answers in Chemistry, like in Mathematics?

 

[lpodtouch]

Does anyone remember what the last short answer question was for chem?

 

[Librah]

Can somebody who got 10.6 for the K question show me how they did it? Thanks

Draw u ice table, change in h2 is 2x=0.36, so x=0.18 change in methanol is -x change in CO is +x. Final mole for H2 is 0.5+0.36, For CO it's 1+0.18 and Methanol 2.5-0.18. Divide all these by 2 because final volume is 2L to get concentration. Then just plug into the K expression.

 

[malcolm21]

Does anyone remember what the last short answer question was for chem?

wasnt it 6 mark haber process?

 

[malcolm21]

Do you guys think they will give marks for crossed out answers in Chemistry, like in Mathematics?

do they do it in maths? i was asking around from the 2u test and everyone shut me down

 

[lpodtouch]

wasnt it 6 mark haber process?

Oh good just making sure. Thought I missed out on something.

 

[Ekman]

Draw u ice table, change in h2 is 2x=0.36, so x=0.18 change in methanol is -x change in CO is +x. Final mole for H2 is 0.5+0.36, For CO it's 1+0.18 and Methanol 2.5-0.18. Divide all these by 2 because final volume is 2L to get concentration. Then just plug into the K expression.

Also you can just use initial concentrations as pressure does not affect k constant, and so it will remain the same.

 

[apurba]

It's very possible HSC have dungoofed, it has happened before.

True. In 2012

 

[Librah]

Also you can just use initial concentrations as pressure does not affect k constant, and so it will remain the same.

That too, but they gave that the change was 2x=0.36, and it didn't actually say it was at equilibrium at 1 L.

 

[Ekman]

That too, but they gave that the change was 2x=0.36, and it didn't actually say it was at equilibrium at 1 L.

It did say it reached equilibrium. "The mixture was allowed to reach equilibrium" and the initial volume is 1L

 

[Librah]

It did say it reached equilibrium.

It's probably a mistake in the question/ bad chemistry on HSC's part then. Since you get 10 if you do it at 1L and 10.6 at 2L for change of 0.36

 

[Ekman]

It's probably a mistake in the question/ bad chemistry on HSC's part then. Since you get 10 if you do it at 1L and 10.6 at 2L for change of 0.36

Lol strange, I got 10.6 in the exam as the initial K, but after recalculating now I got 10 as well lol