Edexcel - Chemistry Unit 2 - 4 June 2013

For the increasing covalent character question on the multiple choice it was Na, Mg, Al, Si. Silicon dioxide has completely covalent bonds and Al compounds' boiling point increases due to increasing covalent character - the Al3+ cation, being highly charged in nature (has a high charge density), is able to polarise the electron clouds of the anion to such an extent that electrons become shared between Al and the anion. The result is a compound with a strong covalent character.

Reply 1541

sophiekutie

11

Original post by James A

I don't know why you don't like the idea that they asked these questions. Shouldn't you know the answer to when they ask these kind of questions? Easy marks in the bag or not?

It seems like you're contradicting yourself. Didn't you learn from the previous mark schemes that it is related to the size of the cation, hence it's ability to polarise the anion cloud of electrons.<<<<< Isn't this classed as recalling information?

I'm sorry if you didn't agree with the material that Edexcel included in this paper, but it's one of those things. It didn't have impossible questions however it did have questions to test the A grade students, sadly, that's how low A-levels have become these days, but recalling info is part of the agenda and it's just gotta be done I'm afraid, all we can do is hope for the best and concentrate on our next exam.

Haha I wasn't insulting you dude! Just saying what I think
And yes although you are recalling information for that last part, you are APPLYING it to a situation and explaining about it.

Reply 1542

sophiekutie

11

Original post by geor

My school was the same! People got really confused!

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Thanks! Haha nice to see someone agrees! :smile:

I guess some schools are taught differently? Some teachers like to make sure the students know every detail of the syllabus whilst some like us to really understand what we're doing :smile:

just different teaching styles

Reply 1543

Kurraiyo

7

The paper really was testing memory and knowledge over a wide range of topics, and I didn't mind that. It's section C that I didn't like, that four marker at the end. I HAD NO IDEA what to write! I babbled on about how burning fossil fuels releases excess CO2 in the atmosphere (pretending not to know that it releases water as well...), that this is an anthropogenic climate change, and that when H2O levels in the atmosphere get too high it comes down as rain, and this is a natural climate change. .___________.

Reply 1544

phaseshift

12

Original post by Kurraiyo

The paper really was testing memory and knowledge over a wide range of topics, and I didn't mind that. It's section C that I didn't like, that four marker at the end. I HAD NO IDEA what to write! I babbled on about how burning fossil fuels releases excess CO2 in the atmosphere (pretending not to know that it releases water as well...), that this is an anthropogenic climate change, and that when H2O levels in the atmosphere get too high it comes down as rain, and this is a natural climate change. .___________.

I thought it was a 'funny' paper, not bad, not great. I know there's a split opinion on the testing of the carbonates, given that the first question (21.d.i) asked: "How could you distinguish between the two powders by heating them?", to which I explained the flame test colouring. Although others have spoken about the thermal decomposition?

Following on from that with question 21.d.ii where we needed to "Suggest another test, other than heating or the use of acid, which could be used to distinguish between magnesium carbonate and barium carbonate. State the results for both compounds." and given that it said, without the use of heat or acid, I went with a simple solubility test. :s-smilie:

Not sure how it went in all fairness, the MCQs were fairly alright though.

Reply 1545

kevsamuel

For the Magnesium and calcium carbonate test where it said how we would identify which if which. (without heating or adding acid). I mistook what they meant by heating and assumed that heating was got to do with flame test .... But I said by adding water and testing the solubilty in water and the magnesium carbonate would dissolve quicker... what I get a mark for that?

Reply 1546

GCSE-help

6

Guys I really think they'll accept either substitution mechanism for that Section B question. I might be being a bit optimistic though as I did Sn2.

What's the general consensus around here?

Reply 1547

phaseshift

12

Original post by GCSE-help

Guys I really think they'll accept either substitution mechanism for that Section B question. I might be being a bit optimistic though as I did Sn2.

What's the general consensus around here?

The question quotes "Use curly arrows to show the movement of electron pairs." which suggests they want the -OH attacking the carbon.

Original post by kevsamuel

For the Magnesium and calcium carbonate test where it said how we would identify which if which. (without heating or adding acid). I mistook what they meant by heating and assumed that heating was got to do with flame test .... But I said by adding water and testing the solubilty in water and the magnesium carbonate would dissolve quicker... what I get a mark for that?

I've done exactly the same as you, flame tests for the first 2-marks and then a solubility test for the second 2-marks. Not sure about the marking though.

Reply 1548

metaltron

11

Original post by GCSE-help

Guys I really think they'll accept either substitution mechanism for that Section B question. I might be being a bit optimistic though as I did Sn2.

What's the general consensus around here?

Surely they will because it will react in both ways if the conditions are right!

Personally, I didn't like the paper. Mainly because it was mostly easy with a handful of hard questions, the worst kind of exam.

Reply 1549

xstarsx67

Guys you know for the barium and water reaction...what was the equation? Cos I think I got it wrong.... :/

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Reply 1550

Kurraiyo

7

Original post by xstarsx67

Guys you know for the barium and water reaction...what was the equation? Cos I think I got it wrong.... :/

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Ba + 2H2O --> Ba(OH)2 + H2

Reply 1551

Al_Chemist

1.

Original post by beaver_tron

Nice, only got this one right because I could remember reading a paragraph about hydration energies in Facer.

Is there an unofficial mark scheme up yet? If so, link please?

An incomplete mark scheme :

http://www.thestudentroom.co.uk/showthread.php?t=2372956

Reply 1552

Londrinna

Original post by StUdEnTIGCSE

Yes but many of the questions was repeated from the past papers. eg the accuracy and reliability of the titration.

Yes that's true, I liked that one :biggrin:

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Reply 1553

sophiekutie

11

Original post by geor

Yeah definitely. My school focused on us really understanding the syllabus, so we spent a lot of time on the organic chemistry. We did hardly any experiments or theory on the group 2/7 stuff however.

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Yeah same! Haha :smile:

. Well fingers crossed for you

Reply 1554

Londrinna

Original post by James A

I think the paper was a very fair one. There were more recall questions than other papers. When I mean recall, I mean stuff like tests for compounds. Chemical equations etc

Yh! Agree, there were many "test for compounds" questions

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Reply 1555

Al_Chemist

Original post by GCSE-help

Yes I think so, because the halides get bigger so they can be more easily polarised, as bigger anions are easier to polarise. It was a tricky question.

And to be honest, I don't remember what I put, but I think your point about the going down group 1 argument is wrong. I may be wrong though :colondollar:

A cation, with a high charge density are very polarising, so will draw electrons towards them with high strength from a large anion, forming a covalent bond, in which this characteristic increases as the anion becomes larger, eg AlI3 has forms a bond with greater covalent character than AlCl3
due to the larger I- anion.

Reply 1556

sophiekutie

11

By the way, for the flame tests should the 2 colours be white and blue?

Reply 1557

GCSE-help

6

Original post by sophiekutie

By the way, for the flame tests should the 2 colours be white and blue?

Colourless and Green

Reply 1558

JaloD

Do you think I would get the marks for saying that MgCo3 is soluble and baCo3 isnt? im referring to the question that asked you to determine between the two, I didn't want to write flame test because it said other than heating.