Chemistry: Post your doubts here!

[areeba240]

how should it be?

 

[Myaaa_20]

Hi, can someone help me with June 2008 Paper 5 Q2 part f please?

 

[unutbenit]

how to do Question 1 ,part d (i)

 

[AnonymousX9]

Guys O/N 2015 P52 q2b part ii, please help. How do I draw the 2 best fit lines and MS even says something about horizontal line???

 

[HELLNO]

how to do Question 1 ,part d (i)

Moles of Iodine in the original solution= 0.2*50/1000=1x10-2
Moles of Iodine in the 10cm3 portion=1x10-2*(10/100)=1x10-3

The ratio of iodine:thiosulfate is 1:2
Therefore number of moles of thiosulfate= 1x10-3*2=2x10-3

Volume of 0.1 mol/dm3 thiosulfate= (2x10-3/0.1)*1000 (From the formula, volume=(moles*1000)/concentration)
Answer is 20 cm3

 

[HELLNO]

Guys O/N 2015 P52 q2b part ii, please help. How do I draw the 2 best fit lines and MS even says something about horizontal line???

When you plot you will get 2 patterns shown on the graph. One horizontal and the other slant line.
Draw to different lines (one for the slant and one for the horizontal)
Extend both of the lines until they intersect, find the x value of the point of intersection.
I got 0.0248 (answers will obviously differ by a specific range)

 

[AnonymousX9]

When you plot you will get 2 patterns shown on the graph. One horizontal and the other slant line.
Draw to different lines (one for the slant and one for the horizontal)
Extend both of the lines until they intersect, find the x value of the point of intersection.
I got 0.0248 (answers will obviously differ by a specific range)

I draw the horizontal line where the y value becomes same right? Like last 2-3 points?
But MS says 2 straight lines and then level off, do I need to draw 2 slanting "best fit" lines through the first few points excluding the horizontal points??? Or just simply 2 lines, one slanting and one horizontal??

 

[HELLNO]

I draw the horizontal line where the y value becomes same right? Like last 2-3 points?
But MS says 2 straight lines and then level off, do I need to draw 2 slanting "best fit" lines through the first few points excluding the horizontal points??? Or just simply 2 lines, one slanting and one horizontal??

Yes exactly last 3 points!
No no, just one best fit slant, and one horizontal (Last 3 points).... Like total of 2 best fits as the questions asks. And record the x value of the point of intersection.

 

[AnonymousX9]

Yes exactly last 3 points!
No no, just one best fit slant, and one horizontal (Last 3 points).... Like total of 2 best fits as the questions asks. And record the x value of the point of intersection.

Okay thank you so much. How's your prep for tmrw's p5? I'm writing paper 52, wbu? I've done papers only from 2014-2016. Any tips?

 

[techgeek]

Okay thank you so much. How's your prep for tmrw's p5? I'm writing paper 52, wbu? I've done papers only from 2014-2016. Any tips?

Though 2 years aren't much but I did like from 2010, and the lastest ones are more important, so you'd do fine.
Did you do all variants?

Also any idea, how do we keep reactants separate until the reaction starts?
like maybe tie a thread to crucible and put the bung. then use thread to empty it. I think I read something like that

 

[student2]

ny1 knws hw to measure effect of temp on solubilty?? i knw hw to do measure effect of conc. on solubilty..

 

[HELLNO]

Okay thank you so much. How's your prep for tmrw's p5? I'm writing paper 52, wbu? I've done papers only from 2014-2016. Any tips?

You got my inbox right? I am not allowed to post long passages, I don't even know why!

 

[HELLNO]

Also any idea, how do we keep reactants separate until the reaction starts?
like maybe tie a thread to crucible and put the bung. then use thread to empty it. I think I read something like that

Draw a glass lid in between both the reactants, that can be dragged up for them to come in contact!
OR
You can keep one reaction in some small cylinder which is attached to a small string. To start the reaction, the string is pulled, and the cylinder falls, causing the reactants to mix.

 

[Rizwan Javed]

Though 2 years aren't much but I did like from 2010, and the lastest ones are more important, so you'd do fine.
Did you do all variants?

Also any idea, how do we keep reactants separate until the reaction starts?
like maybe tie a thread to crucible and put the bung. then use thread to empty it. I think I read something like that

Draw a glass lid in between both the reactants, that can be dragged up for them to come in contact!
OR
You can keep one reaction in some small cylinder which is attached to a small string. To start the reaction, the string is pulled, and the cylinder falls, causing the reactants to mix.

I also read another method somewhere. That is to use a DIVIDED FLASK to separate the reagents. To start the reaction, just stir the flask, reactants will be mixed, and the reaction will start.

 

[HELLNO]

I also read another method somewhere. That is to use a DIVIDED FLASK to separate the reagents. To start the reaction, just stir the flask, reactants will be mixed, and the reaction will start.

How do we draw this

Plus the 2nd one I wrote was your method!!

 

[Rizwan Javed]

How do we draw this

Plus the 2nd one I wrote was your method!!

Divided flask is like this : usually used to separate SOLID reactant from the LIQUID reactant. Used in those experiments for example: CaCO3 reacting with HCl etc.

haha xD yes!

 

[HELLNO]

Divided flask is like this : usually used to separate SOLID reactant from the LIQUID reactant. Used in those experiments for example: CaCO3 reacting with HCl etc

Oh its basically like glass lid, I mean this is how I usually draw it, without knowing that tis actually exist
But yah thanks

 

[Rizwan Javed]

Oh its basically like glass lid, I mean this is how I usually draw it, without knowing that tis actually exist
But yah thanks

Yes But here you don't need to pull up that lid. That BARRIER is FIXED. You just need to stir the flask to start the reaction. Pretty simple than pulling up the lid, or pulling the thread

 

[HELLNO]

Yes But here you don't need to pull up that lid. That BARRIER is FIXED. You just need to stir the flask to start the reaction. Pretty simple than pulling up the lid, or pulling the thread

Oww I see, thats nice!! I will label it as a divided flask right? And the examiner can later google it

 

[Rizwan Javed]

Oww I see, thats nice!! I will label it as a divided flask right? And the examiner can later google it

yes you should write it/label it as divided flask It's actually a standard laboratory equipment.