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Chemistry: Post your doubts here!

F

Fardeen3342

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Error Syntax said:
The reason I choose KCL was that it required the least amount of moles as compare to others, like the concentrations were given so you could calculate the amount required and because it was talking about cation as well.
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So in the question I recall kcl having lesser moles to make a PPT and alcl3 had the most required moles for the positive ion fe203
In the next part the asked for arsenic saying it's negatively charged and said which one will be more efficient . So if alcl3 needed the most moles for the positive ion to form a PPT hence it would need the least for negative ion hence I wrote alcl3 I related it to the I - and s2O8 - reaction we learnt in theory that says similar charge reactions are less feasible .
 
anastasia grey113

anastasia grey113

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Fardeen3342 said:
So in the question I recall kcl having lesser moles to make a PPT and alcl3 had the most required moles for the positive ion fe203
In the next part the asked for arsenic saying it's negatively charged and said which one will be more efficient . So if alcl3 needed the most moles for the positive ion to form a PPT hence it would need the least for negative ion hence I wrote alcl3 I related it to the I - and s2O8 - reaction we learnt in theory that says similar charge reactions are less feasible .
Click to expand...
YESSSSS THAZ EXACTLY Y I CHOSE ALCL3.
 
Anas Patel

Anas Patel

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For why to use digital probe thermometer instead of lab thermometer, I wrote because it has less % error since lab thermometer is 1 dp and digital is 2 dp.
For why the B.P is not 100C but 99.48C, I wrote heat is lost to surroundings.
For the 2nd Q, 1st part, I wrote the more no. Of moles means Delta Twill increase. Since DeltaT is difference between temp of water, which is constant, and temp of solution, the temp of solution increases. So temperature increases as pressure decreases.
For 1st question 1 st part, I wrote Precaution as wear gloves.
For 2nd part, no change at positive electrode and red at negative.
The salt I chose in the experiment 1 and experiment 2 question (Last question of that page I guess, 2 marks) was KCl.
Mass of K2SO4 was around 1.743 g???
Volume needed to dilute was 5 cm3???
For the preparation of solution from mass Of K2SO4, I wrote: Add 1.743 g of K2SO4 To a beaker. Add 50cm3 of water using a burette. Transfer the contents to a volumetric flask. Rinse the beaker. Stopper the flask and shake thoroughly. Add 50 cm3 of water again using a burette to the volumetric flask. Stopper the flask and shake thouroughly.
For the apparatus needed to measure that 5cm3 , I wrote a graduated pipette.
For the question on Expermient1 and experiment 2, which was what happens when you increase the charge from -1 to -2 to -3, I wrote: As the charge becomes more negative, the amount of salt needed to precipitate 1dm3 sol decreases. This is because the concentration of ions increases.
 
anastasia grey113

anastasia grey113

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IwanttopassAlevel said:
any last minute help on cie a level chemistry paper 5
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just revise all the past papers
don't attempt them...just go thru the past questions from 15 to 17 (since they r the latest and one's most according to our syllabus)
find online notes here and there if u can tho i dint use any
m assuming youve already gone thru the book but if u havent id suggest reading the chapter about practical skills from the book
go to chemguideforcie.co.uk if u want to cuz thaz where u can find the best notes for anything related to A Levels chem

but if u dont have the time, just going thru the papers will help
 
I

IwanttopassAlevel

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anastasia grey113 said:
just revise all the past papers
don't attempt them...just go thru the past questions from 15 to 17 (since they r the latest and one's most according to our syllabus)
find online notes here and there if u can tho i dint use any
m assuming youve already gone thru the book but if u havent id suggest reading the chapter about practical skills from the book
go to chemguideforcie.co.uk if u want to cuz thaz where u can find the best notes for anything related to A Levels chem

but if u dont have the time, just going thru the papers will help
Click to expand...
Thanks. did you do 51 or 52
 
H

hamadh

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Can somebody please explain me how can the two structures be optical isomers. I mean shouldn't the carboxylic grip on the upper side in the second structure face the opposite side to the left I mean. The same applies for the OH in the carboxylic group on the mower side in the second structure.
 

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S

Sonata

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Guys i have paper 2 chem in like 2 days. Well i'm freaking out. Anyone else taking it? Tips?????
 
anastasia grey113

anastasia grey113

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Sonata said:
Guys i have paper 2 chem in like 2 days. Well i'm freaking out. Anyone else taking it? Tips?????
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well m doing A Levels at the moment
but yess in the last days u r not supposed to do much
just attempt the past papers and read the book n all thruout the year
but for now just relax or go thru ur solved past papers and that's that
and see where u made mistakes in the solved papers
 
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