AS Chemistry, OCR A, 17/05

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Nikta.Shf
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#1
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#1
How did you find the exam today?
what did you guys put for that 5 marker about recognizing B and C that were metal halides. (specifically the test? did you talk about silver nitrate and then the concentration test with ammonia?)
also what value did you get for the enthalpy of neutralization?
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Papucito
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Bro , wtf
We talking about As 8CH0/01 2022 right ?
That was soo different to all other pastpapers man , not a single definition questions barely any questions to score marks
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superharrydude09
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The range for molecular mass was 100-115, meaning it can't be iodide ions, so do silver nitrate test to differentiate between chloride/bromide solutions. You don't need the ammonia test here, if you have Br of mass around 80, so it must be group 1, (Bi2X would have too much mass, where X is a group 2 element), and the only group 1 metal with the right mass is Na, so NaBr is one compound, doing a similar process to Cl gives CaCl2
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_ryan_27
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(Original post by superharrydude09)
The range for molecular mass was 100-115, meaning it can't be iodide ions, so do silver nitrate test to differentiate between chloride/bromide solutions. You don't need the ammonia test here, if you have Br of mass around 80, so it must be group 1, (Bi2X would have too much mass, where X is a group 2 element), and the only group 1 metal with the right mass is Na, so NaBr is one compound, doing a similar process to Cl gives CaCl2
You're definitely right on the Iodide inference but:
-How come do you not need the ammonia test? Differentiating between the white ppt AgCl forms and the "cream" precipitate AgBr forms can be quite difficult, in terms of practicality.

lol I guess I never thought about predicting the actual identities of the molecules- I only outlined how u could deduce the compounds. Oh well.
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HELPBISH
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#5
Was the advanced information accurate?
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_ryan_27
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(Original post by HELPBISH)
Was the advanced information accurate?
For the most part- yes. They did ask a few questions that weren't on the advanced info but they were limited to around 2-3 marks per q and there were only a few I can remember that weren't on the advanced info.
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superharrydude09
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(Original post by _ryan_27)
You're definitely right on the Iodide inference but:
-How come do you not need the ammonia test? Differentiating between the white ppt AgCl forms and the "cream" precipitate AgBr forms can be quite difficult, in terms of practicality.

lol I guess I never thought about predicting the actual identities of the molecules- I only outlined how u could deduce the compounds. Oh well.
You make a fair point, I kinda assumed that the student would have good enough eyes to differentiate between cream and white.
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_TheDon
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Nah u need the ammonia part definately
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maariah2510
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#9
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(Original post by Nikta.Shf)
How did you find the exam today?
what did you guys put for that 5 marker about recognizing B and C that were metal halides. (specifically the test? did you talk about silver nitrate and then the concentration test with ammonia?)
also what value did you get for the enthalpy of neutralization?
for halides the group 2 one i got cacl2 and the group 1 i got NaBr - apparently you had to work out the compounds. also, the first part of q=mct was -116 and second part was -58 for the neutralisation bit
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maariah2510
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(Original post by maariah2510)for halides the group 2 one i got cacl2 and the group 1 i got NaBr - apparently you had to work out the compounds. also, the first part of q=mct was -116 and second part was -58 for the neutralisation bit

also, you would talk about tests with silver nitrate and dilute and conc ammonia inlcuded and colours of precipitates
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_TheDon
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#11
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The thing is THat question never said Work out compounds b and c, But U should I guess idk
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