Edexcel - Chemistry Unit 2 - 4 June 2013

Reply 1580

Maybenexttime

Original post by samsimmons

Would did you guys put for the equation in section C?
I did Cl2(g) + 2Br-(aq) --> Br2(aq) + 2Cl-(aq)

Yeah I put exactly the same. ^^

Reply 1581

phaseshift

12

Original post by Maybenexttime

I wrote for the flame test magnesium producing a bright white flame and barium green...o.O

Whenever I've done magnesium flame tests in practicals that's what I'd gotten, and it's what the CGP revision guide says...I have no idea what the mark scheme says for magnesium flame colour though, anyone know?

Well the George Facer book suggests that Magnesium compounds burn in a "brilliant white flame" but past mark schemes have been strict allowing only "no colour" in some cases. We'll need to wait for the mark scheme, you are correct with respect to barium though.

Original post by samsimmons

Would did you guys put for the equation in section C?
I did Cl2(g) + 2Br-(aq) --> Br2(aq) + 2Cl-(aq)

Yah.

Reply 1582

zyxwvuts

1

Original post by Maybenexttime

Yeah I put exactly the same. ^^

Great

What did you get for the organic questions?

I put ethanol and aqueous conditions. And then elimination for the reaction type. I did the Sn1 mechanism.
For the colour changes of the alcohols I said orange to green for the secondary and remains orange for the tertiary. The structural formula I did was CH₃COCH₂CH₃I think.

Reply 1583

Locked_box

6

Original post by xstarsx67

For the titration indicator colour, I think I just put colourless, instead of x to colourless...would I still get the mark? I could have sworn it said 'colour at the end point if indicator wasn't used?

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I did that too...I think I did that for the bromine question as well. I just think I remember the question saying what colour is the end point or what colour would you observe so I'm hoping that just saying colourless is fine :smile:

Reply 1584

kevsamuel

Original post by beaver_tron

Hate to say it, but the second bit definitely wouldn't, it should be assumed they are doing so. If they question were, what could be a source of error, that would be a valid answer.

I think, if I remember properly, I put that you divide the excess into portions, this lowers accuracy, increases reliability, the percentage error increases, but you can eliminate anomalies and take an average.

oh well, thanks anyway :smile:

how many marks was that question? just one right?

Reply 1585

Goods

16

Original post by Maybenexttime

I wrote for the flame test magnesium producing a bright white flame and barium green...o.O

Whenever I've done magnesium flame tests in practicals that's what I'd gotten, and it's what the CGP revision guide says...I have no idea what the mark scheme says for magnesium flame colour though, anyone know?

Magnesium produces a colourless flame

Posted from TSR Mobile

Reply 1586

xstarsx67

Original post by James A

Not sure about that :s-smilie:

I don't think so :frown:

Did the question say barium hydroxide with HCl ?

Ah good point - no I remember it saying the product produced in a)(ii) - obviously if it had written barium hydroxide than i would have noticed my stupid mistake and corrected it lol :/ so hopefully I'd get the mark? That's a tough one tho :frown:

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Reply 1587

Goods

16

Original post by geor

The more I think about it the more I think flame test will be accepted. I think by it saying without heat or acid it just meant it wanted you to not put one of the two tests in the previous questions. Terribly worded question if so!

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I checked the AS practical skills book and theres nothing about analysis based of conductivity or solubility. Therefore it has to be flame tests because there are no other tests on the AS course that could be used.

Reply 1588

Meehar17

wait I am so confused about the magnesium and barium carbonate question.... how why the hell do you use a flame test when the question said without heat? and also if you guys are saying that you can use a flame test then why cant you out thermal decomposition as well.

Reply 1589

xstarsx67

Original post by Locked_box

I did that too...I think I did that for the bromine question as well. I just think I remember the question saying what colour is the end point or what colour would you observe so I'm hoping that just saying colourless is fine :smile:

Yeah hopefully *fingers crossed* I can picture the mark scheme saying:
(Pale yellow) to colourless - 1 mark
Meaning colourless would defo get the mark...here's to positivity! :wink:

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Reply 1590

phaseshift

12

Original post by Goods

I checked the AS practical skills book and theres nothing about analysis based of conductivity or solubility. Therefore it has to be flame tests because there are no other tests on the AS course that could be used.

Original post by Meehar17

wait I am so confused about the magnesium and barium carbonate question.... how why the hell do you use a flame test when the question said without heat? and also if you guys are saying that you can use a flame test then why cant you out thermal decomposition as well.

A valid point you have there. Goods, care to lend us your logic?

If you stick a lump of carbonate in a flame, you are heating it, you're introducing heat - thats the whole premise of the flame tests. :s-smilie:

(edited 10 years ago)

Reply 1591

Meehar17

Original post by HarryMWilliams

A valid point you have there. Goods, care to lend us your logic?

If you stick a lump of carbonate in a flame, you are heating it, you're introducing heat - thats the whole premise of the flame tests. :s-smilie:

but if you put the powder in the flame, you are also heating it aren't you

Reply 1592

jollygood

8

Original post by Meehar17

wait I am so confused about the magnesium and barium carbonate question.... how why the hell do you use a flame test when the question said without heat? and also if you guys are saying that you can use a flame test then why cant you out thermal decomposition as well.

Exactly I just don't understand why everyone is saying Although the question said without heating but still it should be a flame test.

Reply 1593

Maybenexttime

For the two features of a dynamic equilibrium my 1st point was: "The forward reaction occurs at the same rate as the backward reaction resulting overall in no net change", and then the only other feature of a dynamic equilibrium I could think of was: "In a closed system", which is highly unlikely to be on the mark scheme seeing as the reaction is between the air and the sea! Fml haha.

Reply 1594

jollygood

8

What I did for MgCO3 and BaCO3 question in first part I wrote the equation and said that on giving the same amount of heat to both carbonates, Mg carbonate lump will break and bubbles of gas can be seen rising if u do it properly like collecting gas above water. but on providing same amount of heat there will be no gas produced. and u can check it b y lime water. I just wrote it to be on safe side. In the next part without HEATING one I said the TEST WITH LIME WATER. and said as a continuation of first part that the gas collected already can turn lime water milky in case of magnesium carbonate but not in case of barium carbonate.

Reply 1595

Meehar17

Original post by jollygood

Exactly I just don't understand why everyone is saying Although the question said without heating but still it should be a flame test.

but why is it a flame test and not thermal decomposition? either way you are heating the carbonate

Reply 1596

F1's Finest

21

Hopefully they accept flame test, but I know it's wrong! haha

They will be looking for solubilities!

Reply 1597

zyxwvuts

1

For the iodine colour change one, do you think they will accept brown to colourless? :frown:

Reply 1598

jollygood

8

Original post by Kurraiyo

I was pretty sure it was 29 but you confused me now XD

LOoool u confused me for a moment I thought to confuse you aswell. it happens that when u listen to other peoples answers u think u have done that question wrong. I am not too sure about this TBH.

Reply 1599

kevsamuel

is magnesium carbonate more soluble in water than calcium carbonate?

Edexcel - Chemistry Unit 2 - 4 June 2013

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