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Original post by ADAOBI123
The questions today were out to trick us ! :mad:


yeah. But still better than the past papers i thought
Original post by Freddy-Francis
yeah. But still better than the past papers i thought


really ? I thought the past papers were way easier than the exam !
This was a paper where if you didnt do all the past papers and remember markschemes,you'd be fu**ked
anyone doing the markscheme?
ill help on the ones i remember.
I don't think anyone's bothered to do it but I don't mind starting one with help
Original post by jackitsme
This was a paper where if you didnt do all the past papers and remember markschemes,you'd be fu**ked


Interestingly I would disagree. I did only about 3 past papers but instead focused on the specification and to my knowledge only dropped 4 marks. I guess chemistry is just a subject where you have to apply your knowledge in different situations and some of these in this exam made you prone to mistakes. I'm sure you did great though anyway :smile:
Original post by Nermin Hayek
I don't think anyone's bothered to do it but I don't mind starting one with help


1a) Define relative isotopic mass. (2)the mass of an atom of an isotope compared with 1/12 of the mass of an atom of c-12
1b) Fill the table in for the atomic structure of a potassium atom and ion. (3)
1c) How many molecules are in 6.(something)g of SiCl4? (3)
1d) Draw the symbols for each particle shown in the ionic lattice structure of KCl. (2)

3a) A precipitation reaction was used to identify the iodide present in Potassium Iodide. State the reagent used for this reaction (1)agno3
3b) Write the ionic equation to show the reaction between this reagent and the Iodide ion, including state symbols. (2)ag+(aq) + i-(aq)= agi(s)
3c) What colour would the precipitate containing the iodide ion show? (1)yellow
3d) A mixture of potassium iodide and bromine was present in a solution. What solvent can be used to identify the presence of iodide in this solution? (1)conc nh3

5a) Describe the reactivity of the group 2 metals with chlorine as you descend the group. (5)
-increase nuclear charge outweighed by increase atomic radius
-more shells;more electrons;more inner shielding effect by inner electrons;
decrease nuclear attraction. easier to remove outer elect to react with halogens. reactivity increases

5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)both covalently bonded to carbon(unsure)
5c) Fill the boxes in of the table stating the properties of lithium, carbon and fluorine (6)

A few other random questions I can remember (in any order):

- A student suggested the bond angles in H-N-H would be larger in NH3BF3 than NH3, suggest why. (3 marker I think)
- What bond angles are present in the F-B-F in: i) BF3 ii) NH3BF3 (2)
- Phosphene gas reacts with oxygen to form P4010 and water. Write out the equation for this reaction. (1)
- Why does PH3 have a lower boiling point than NH3? (1)
- Why is N2SO4 described as a salt? (1)
- State the main types of intermolecular forces in NH3 and PH3 (2)
- Give the equation for the reaction between Aluminium Oxide and sulphuric acid, including state symbols. (2)
- Work out the number for X in (metal).XH2O 0.321/ 0.0200= 16
- Using oxidation numbers, state why the reaction of P4 was a disproportionation reaction (3)
- Write out the equation for the reaction between Chlorine and water. Explain why the litmus paper turned red. (2)acid produced, ph decreases, increas in h+
- Define 'dative covalent bond'. (1 or 2?)sharing of a pair of electrons between 2 covalently bonded atoms where one of the atoms supplies both electrons.
- Using dot and cross diagrams, draw the bonding in NH3BF3 and label the dative covalent bond. (2)

i was going to do a bit more but i have decided its probably best to concentrate on f322,f324 and f325 lool.
(edited 10 years ago)
Original post by scorpio22
anyone doing the markscheme?
ill help on the ones i remember.


It was started around page 40 ish but it was too difficult to remember specific question numbers and marks per question so we gave up. Sort of really need the paper in order to compile the unofficial markscheme.

edit: (^^I stand corrected)
Reply 1088
A:46
b:41
c:36
Original post by Nath_an
A:46
b:41
c:36


i was thinking A is 50 from this time last year and jan 13
Original post by adaobi123
i thought it was okay, made silly mistakes here in and there, i'll probably end up with b if not a c.


ffs sorry that was my friend
(edited 10 years ago)
Original post by ADAOBI123
just hope unit 2 is better

same
Original post by scorpio22
3d) A mixture of potassium iodide and bromine was present in a solution. What solvent can be used to identify the presence of iodide in this solution? (1)conc nh3


Surely the answer to that should be cyclohexane?

I know chloride and bromide compounds/precipitates will dissolve in different concentrations of NH3 (Iodide compounds won't dissolved). However it is already in solution, so surely the best noticeable identification would be to mix the halogen solution with cyclohexane, producing a violet/lilac layer.

I put cyclohexane, seemed more obvious to me as with NH3 i thought it would be harder to identify as it is already in solution.

Edit: fyi it might not be your answer, life's too short to trawl through 20 pages from only 3 hours after the exam :P

Anyhow, this is what i would've put;

Also other answers i would change or add to the student made MS (personal answers not necessarily correct)

5b) State why using graphite or diamond for the first ionisation energy for carbon was (unnecessary?) (1)both covalently bonded to carbon(unsure) First ionisation energy applies to atoms of elements in gaseous state.

Why is Na2SO4 described as a salt? The H+ ions in the sulfuric acid have been replaced by the positive Na+ ions.
(edited 10 years ago)
Reply 1093
Original post by _Morsey_
Surely the answer to that should be cyclohexane?

I know chloride and bromide compounds/precipitates will dissolve in different concentrations of NH3 (Iodide compounds won't dissolved). However it is already in solution, so surely the best noticeable identification would be to mix the halogen solution with cyclohexane, producing a violet/lilac layer.

I put cyclohexane, seemed more obvious to me as with NH3 i thought it would be harder to identify as it is already in solution.


It only is natural to follow the Silver Nitrate Test with the addition of Aqueous Concentrated Ammonia when evaluating contamination - such as the context of the question - or to distinguish Chlorine and Bromine as their colours are sometimes harder to differentiate.


Posted from TSR Mobile
(edited 10 years ago)
Reply 1094
Original post by Ché.
It only is natural to follow the Silver Nitrate Test with the addition of Aqueous Concentrated Ammonia when evaluating contamination - such as the context of the question - or to distinguish Chlorine and Bromine as their colours are sometimes harder to differentiate.


Posted from TSR Mobile





Posted from TSR Mobile
Original post by Ché.
It only is natural to follow the Silver Nitrate Test with the addition of Aqueous Concentrated Ammonia when evaluating contamination - such as the context of the question - or to distinguish Chlorine and Bromine as their colours are sometimes harder to differentiate.


Posted from TSR Mobile


From what i remember, it was a completely different question unrelated from when it asked about Silver Nitrate Test. If it was, then surely it wouldn't be a solution of Potassium Iodide and Bromide (as stated in the question), but a solid precipitate of iodine and bromine based compounds?
Original post by _Morsey_
Surely the answer to that should be cyclohexane?

I know chloride and bromide compounds/precipitates will dissolve in different concentrations of NH3 (Iodide compounds won't dissolved). However it is already in solution, so surely the best noticeable identification would be to mix the halogen solution with cyclohexane, producing a violet/lilac layer.

I put cyclohexane, seemed more obvious to me as with NH3 i thought it would be harder to identify as it is already in solution.

Edit: fyi it might not be your answer, life's too short to trawl through 20 pages from only 3 hours after the exam :P


I think the reason is this, if you added cyclohexane as you are aware it forms pale green, orange and violet, but imagine if the solution was contaminated. There is no way you could distinctly tell the proportion or relatively the amounts of each ion. You would just get a mix of colours and it would be unclear and inaccurate. By using concentrated ammonia you can definitivly tell if there is alot or a little amount of iodide ions.

All in all it gives you a much better and more accurate estimate than cyclohexane
Reply 1097
Original post by _Morsey_
From what i remember, it was a completely different question unrelated from when it asked about Silver Nitrate Test. If it was, then surely it wouldn't be a solution of Potassium Iodide and Bromide (as stated in the question), but a solid precipitate of iodine and bromine based compounds?


I thought it just had that idiotic verbose part question passage...

I thought the question subsequently followed in the following way: "The student then.... They noticed that...."
Am I wrong!?

Even so, I feel Cyclohexane is for when distinguishing displacement reactions; not necessarily precipitation formation react ions high was clearly stated.

I hope that it is right!
It was only natural! It didn't take long to think of!
If I write something down too fast, it means it definitely is natural!




Posted from TSR Mobile
Original post by _Morsey_
From what i remember, it was a completely different question unrelated from when it asked about Silver Nitrate Test. If it was, then surely it wouldn't be a solution of Potassium Iodide and Bromide (as stated in the question), but a solid precipitate of iodine and bromine based compounds?


Exactly as you just said now infact "but a solid precipitate of iodine and bromine based compounds?". This is the exact reason we use ammonia, because all the bromine ions would dissolve showing us relatively how much iodide ions the solution contained. Cyclohexane infact would not have even worked.
i think i have dropped 10 marks to the most.
15 -18 ums.:O
i need to smash f322 or i am staying at home for the next year and repeating college :O