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AQA CHEM5 A2 Chemistry - 19th June 2013

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Is Chemy five tough
Reply 401
Avatar for Quarky
Quarky
Can someone help me understand this question please?
"Explain why the hydration of the fluoride ion is more negative than the hydration enthalpy of the chloride ion?
Original post by cheesypuff
Is Chemy five tough


I found Chem5 easier than Chem4. But maybe that's just because I'm still in the process of revising for it!
Original post by Quarky
Can someone help me understand this question please?
"Explain why the hydration of the fluoride ion is more negative than the hydration enthalpy of the chloride ion?


Fluoride ions are smaller than chloride ions, and as such have a greater charge density. This means that the negative charge on a fluoride ion attracts the δ+ hydrogen on a water molecule more strongly than that of a chloride ion. Hence, more negative enthalpy of hydration.
Reply 404
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Quarky
Original post by Tullia
Fluoride ions are smaller than chloride ions, and as such have a greater charge density. This means that the negative charge on a fluoride ion attracts the δ+ hydrogen on a water molecule more strongly than that of a chloride ion. Hence, more negative enthalpy of hydration.

Ahh I see, cheers :smile:
Reply 405
Avatar for Minnie me
Minnie me
Original post by Hamzi


Its on q4 on the June 2011 paper

Here is the link to the paper:
http://filestore.aqa.org.uk/subjects/AQA-CHEM5-W-QP-JUN11.PDF


hi,
this question talks about observations of magnesium and sulfur burning in oxygen.
for magnesium we would observe a vigorous reaction with a bright white flame and white fumes
for sulfur we would observe a blue flame and a choking gas

me :biggrin:
(edited 10 years ago)
Hello
does anyone know what u will se when caoh2 reacts with water and when Caso4 adds to water
Reply 407
Avatar for popnit
popnit
14
Original post by Hamzi
I guess you do because if they give you all the observations for the other period 3 elements with oxygen in the text book then why did they just skip observations for silicon.

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Because it practically doesn't even happen..or infact it is just too slow.
Can anyone tell me why iron (II) needs different amounts of ethanedioate than Cu2+ on titration?
Reply 409
Avatar for Ren_9
Ren_9
HELP! Has anyone found an easy way of memorizing the observations of Acid-Base substitutions of the metal ions Fe(2+) Fe(3+) Co Cu Al Cr(3+) ?

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(edited 10 years ago)
Reply 410
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Ren_9
Original post by popnit
You don't need to know this, it's not even mentioned in the nelson thorne textbook

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Actually if you check part 3.5.2 of the Chem specification it says you how period the elements react with oxygen, limited to the formation of Na Mg Al Si P and S oxides. But you DO NOT need to know how Al203 and SiO2 reacts with WATER as they are INSOLUBLE
SIZE=1]Posted from TSR Mobile
Reply 411
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popnit
14
Original post by Ren_9
Actually if you check part 3.5.2 of the Chem specification it says you how period the elements react with oxygen, limited to the formation of Na Mg Al Si P and S oxides. But you DO NOT need to know how Al203 and SiO2 reacts with WATER as they are INSOLUBLE
SIZE=1]Posted from TSR Mobile


Well spotted!
Reply 412
Avatar for Ren_9
Ren_9
Original post by Lucianaaaa
Can anyone tell me why iron (II) needs different amounts of ethanedioate than Cu2+ on titration?


Are you comparing why Fe2+ and Fe3+ need different amounts and Cu2+ Cu+ doesn't?
Not sure but it might be connected to the density charge on each ion that may cause an already slightly acidic soln. Strong coordinate bonds and weak O-H bonds that cause H to 'fall off'

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Reply 413
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Xiomara
18
Electrochemical cells is nowhere near as bad as I thought it would be! Still haven't fully memorised Transiton Metal complexes though :/
Reply 414
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erniiee
13
Original post by Xiomara
Electrochemical cells is nowhere near as bad as I thought it would be! Still haven't fully memorised Transiton Metal complexes though :/


Strangely for me, Transition metals are my favourite topic. I'm scared to look at redox equilibria and the rest of electrochemistry though :lol:
Has anyone done the isa and if yes, how was it??? Difficult?
Original post by erniiee
Strangely for me, Transition metals are my favourite topic. I'm scared to look at redox equilibria and the rest of electrochemistry though :lol:


I found Unit 5 so so much easier than unit 4. I don't know why.
I hate this unit :angry:
Original post by Mocking_bird
I hate this unit :angry:


You and me both.
Reply 419
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Ren_9
Original post by frogs r everywhere
I found Unit 5 so so much easier than unit 4. I don't know why.


I feel the same way, the only thing is that it's synoptic so in the exam they could ask you about anything from AS and also unit4 :frown:

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