Physics, Chemistry and Biology: Post your doubts here!

The_Boss

The_Boss

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Saad the Paki said:
To distinguish between water and ethanol:
Test : Add magnesium
Water: Bubbles of Hydrogen
Ethanol: No reaction
Acceptable?
Click to expand...
No ethanol reacts with magnesium as magnesium is more reactive than the Hydrogen so displaces it.
Ethanol + Magnesium ---> Magnesium Ethoxide + Hydrogen (Not sure of spelling though)
A better test would be B.P Ethanol more volatile than water
Chemical test would be test pH using "pH meter" and water would have neutral and ethanol more alkaline. Write meter as it would be able to detect slight alkaline solution as well
 
Abdurrahmanmuhammed

Abdurrahmanmuhammed

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The_Boss said:
No ethanol reacts with magnesium as magnesium is more reactive than the Hydrogen so displaces it.
Ethanol + Magnesium ---> Magnesium Ethoxide + Hydrogen (Not sure of spelling though)
A better test would be B.P Ethanol more volatile than water
Chemical test would be test pH using "pH meter" and water would have neutral and ethanol more alkaline. Write meter as it would be able to detect slight alkaline solution as well
Click to expand...
ph meter not possible as both are neutral so cant distinguish but for ethanol and ethanoic acid ph meter is possible!
 
Abdurrahmanmuhammed

Abdurrahmanmuhammed

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Iris Dylan Lane said:
This is from the examiner's report. "Only the most able candidates scored well on this question. Nitrate ions were sometimes
successfully identified but the identity of solution K as a transition metal compound was rare. The
presence of ammonium ions and copper was often given even though the solution was pink to start
with."
The pink solution suggests that copper is NOT present, Copper salt solutions are BLUE.
Hope I'm right. Anyone one is free to correct any errors :)
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lol everyone knows transitions metals are colored but i doubted if i needed to write cobalt or only transition metal
 
M

MariaKhan243

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Chemistry paper 62 m/j 2014 q3 part c
In the mark scheme it says aluminium oxide gives a larger surface area... but can someone explain please?
 
NOneed2speedd

NOneed2speedd

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is my diagram correct? If not please tell me how to draw
(And ignore my drawing i knw it's really bad)
 

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ThePacifics

ThePacifics

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I have chemistry paper 6 tomorw and i need urgent help they r asking me to draw two intersecting straight lines in the graph? How to do tht? I can only see all the points fitting into a single line. how to do the 2 intersecting lines?
 
sj0007

sj0007

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XxChampXx said:
There are two scenarios for this:-

1) Check this paper first(MJ2011 QP61 Q4 e(iii)):- https://drive.google.com/folderview...sp=drive_web&tid=0BzumkDfi9230ajBJb1BVUl8xODg

So in this case the student is pouring solution(for which concentration is being checked) of potassium manganate(VII) from the beaker. Thus, the lesser the volume required for the colour to change, the more concentrated it is.

2)https://drive.google.com/folderview...drive_web&tid=0BzumkDfi9230ajBJb1BVUl8xODg(MJ 2008 QP6 Q4 e(iii))

So in this case the solution for which concentration is being checked is not poured, the known volume is already in the flask. Thus, whatever is being poured, in this case potassium manganate(VII), has to be in larger volume.

So basically you just have to look if the solution checked for concentration(i.e. A and B) has a known volume or not. If it does not, then the one with the smaller difference is more concentrated. If it does have a known volume, then one with larger difference is more concentrated.

Good luck for your exams
Click to expand...
THANKU!!!!!!!
Seriously I was cracking my head open as I have my exam tomorrow but u just solved my problem!!!
Best of luck to u too!!!!!!!
:) :) :) :)
 
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