Chemistry: Post your doubts here!

[LonelyStudent]

best of luck for BIO

You too buddy.

 

[Holmes]

You too buddy.

Thanks! but I am not a Biology student!

 

[Fardeen3342]

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.

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]

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 .

YESSSSS THAZ EXACTLY Y I CHOSE ALCL3.

 

[Error Syntax]

YESSSSS THAZ EXACTLY Y I CHOSE ALCL3.

well there goes my two marks XD. Yeah you guys are right the logic adds up.

 

[anastasia grey113]

well there goes my two marks XD. Yeah you guys are right the logic adds up.

lol its ok
m pretty sure youll do well in p4 to make up for it
thank God m still getting a 25 xD

 

[Anas Patel]

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.

 

[IwanttopassAlevel]

any last minute help on cie a level chemistry paper 5

 

[anastasia grey113]

any last minute help on cie a level chemistry paper 5

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

 

[IwanttopassAlevel]

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

Thanks. did you do 51 or 52

 

[anastasia grey113]

Thanks. did you do 51 or 52

52

 

[IwanttopassAlevel]

was it cool?

 

[anastasia grey113]

was it cool?

well not tough
just different

 

[IwanttopassAlevel]

did it follow amy year pattern

 

[anastasia grey113]

did it follow amy year pattern

nope

 

[Fardeen3342]

did it follow amy year pattern

it followed w 10 or s 1o read those for question 2 the molarity question was very similar to the one that came today

 

[hamadh]

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.

 

[armeena]

lol i gave 51. it was so easy, i'm scared the threshold will be very high.

 

[Tauqir_hamed]

Guys what did you write about what will happen to the temperature of water when sucrose is used instead of glucose, I am talking about varient 52 , question no 2

 

[Sonata]

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