Chemistry: Post your doubts here!

[anonymous1122]

hello, i am just new to this community
i have one question pls
what happens if for titration u don't get ur results the same as the teacher's or it is not within the range of the teacher's? Do u get the whole titration wrong or will there be any error carrried forward marks?
My cousin just took her exam and she is freaking out as she didn't get the same results as the teacher's

3 marks are deducted only

 

[omg]

hello, i am just new to this community
i have one question pls
what happens if for titration u don't get ur results the same as the teacher's or it is not within the range of the teacher's? Do u get the whole titration wrong or will there be any error carrried forward marks?
My cousin just took her exam and she is freaking out as she didn't get the same results as the teacher's

yes , only 3 marks are deducted. she will get marks for the table, headings, calculations and 1 mark for her values.

 

[Maayee]

3 marks are deducted only

so if the all titration question is out of 11 marks, only 3 marks are deducted right?
anyways thank u for ur reply

 

[Maayee]

yes , only 3 marks are deducted. she will get marks for the table, headings, calculations and 1 mark for her values.

ok thankkk u sooo much

 

[anonymous1122]

How many marks would be deducted if i performed the experiment wrong
I didnt add till 45 cm3 as i read it wrong and thought total volume to be 45 cm3 of solution
Would i still be getting marks for graph since i fulfilled all the requirements and 2-3 out of 4 for tabletable and calculations?

 

[Abdel Moniem]

Anyone here appeared for the chemistry practical paper 31?

 

[..sacrifice4Revenge..]

Okay so

Qs:
Acidified solutions of iron(II)salts can be titrated using a dilute solution of potassium manganate(VII) ,KMnO4
Use data to write a balanced equation..

Now Im having confusion in all similar questions.
How do I know which equation to use. Will I use Fe+2 reducing to Fe
Or Fe+3 to Fe+3?

Similarly for Manganate.

A generalized answer would be appreciated.

Also, how much electrode potential difference means that the reaction wont occur, like is there a fixed value?
Like Fe+3 reacts with Cl-
Why wont the react,how will we deduce it from cell equations?

 

[papajohn]

Q8 b(i) part Please anyone explain me???
http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_42.pdf
The Sarcastic Retard
Bilal Khan
Metanoia

 

[Metanoia]

Okay so

Qs:
Acidified solutions of iron(II)salts can be titrated using a dilute solution of potassium manganate(VII) ,KMnO4
Use data to write a balanced equation..

Now Im having confusion in all similar questions.
How do I know which equation to use. Will I use Fe+2 reducing to Fe
Or Fe+3 to Fe+3?

Similarly for Manganate.

A generalized answer would be appreciated.

Also, how much electrode potential difference means that the reaction wont occur, like is there a fixed value?
Like Fe+3 reacts with Cl-
Why wont the react,how will we deduce it from cell equations?

MnO4- is an oxidizing agent, in acidic conditions, it would form Mn2+.
The Fe2+ would in turn be oxidized to Fe3+.

E(cell) = E(reduction) - E(oxidation) > 0 for reaction to be feasible.

 

[Sahan27]

Re: All Chemistry help here!! Stuck somewhere? Ask here!
that's what I think
not sure though
Moles H+ in excess = 0.001
Total volume = 0.035 L
Concentration= 0.001/0.035= 0.0286
s0 -log(0.0286)= 1.54=PH


I am going to give it a try.

Moles HBr = 0.020 L x 0.200 M =0.0040
Moles NaOH = 0.015 L x 0.200 =0.0030

Moles H+ in excess = 0.0010
Total volume = 0.015 L
Concentration H+ = 0.0010 / 0.015 =0.0667
pH =-log ( 0.06667)
=0.176

 

[student8]

hello, i am just new to this community
i have one question pls
what happens if for titration u don't get ur results the same as the teacher's or it is not within the range of the teacher's? Do u get the whole titration wrong or will there be any error carrried forward marks?
My cousin just took her exam and she is freaking out as she didn't get the same results as the teacher's

You'll only lose the marks for accuracy.

 

[student8]

How many marks would be deducted if i performed the experiment wrong
I didnt add till 45 cm3 as i read it wrong and thought total volume to be 45 cm3 of solution
Would i still be getting marks for graph since i fulfilled all the requirements and 2-3 out of 4 for tabletable and calculations?

It depends how much marks they have allocated for the accuracy and according to that , the examiner will deduct the marks..its not hard and fast rule tht they'll only deduct 3 marks.
yeah you'll.

 

[Abdel Moniem]

hello, i am just new to this community
i have one question pls
what happens if for titration u don't get ur results the same as the teacher's or it is not within the range of the teacher's? Do u get the whole titration wrong or will there be any error carrried forward marks?
My cousin just took her exam and she is freaking out as she didn't get the same results as the teacher's

is that paper 31?

 

[student8]

Can anyone plz explain me in detail about the differences b/w
1. covalent bonding
2. ionic bonding
3.hydrogen bonding ( and how and why hydrogen bonds are formed) ?

Help will be appreciated.

 

[liptonice]

guys M/J paper 11 2010 question 4 and 5
please help guys !! thanks much appreciated !!!
I dont know how to insert the image as photo and cropping,, so I just uploaded one page from questions.

 

[Abdel Moniem]

Can i explain that CCl4 is not hydrolysed by water because of the smaller atomic radius so the lone pair of the water molecules cannot be donated to the vacant d orbitals.

 

[NIM]

9701/43/O/N/11
Question no 5 part b iv
Need help!!!

 

[tiki-taka]

how to find the other element

 

[Debonny1]

http://maxpapers.com/syllabus-materials/chemistry-9701-a-level/attachment/9701_w14_qp_41/ q1a(ii)... Why do we multiply by 27??

 

[The Sarcastic Retard]

guys M/J paper 11 2010 question 4 and 5
please help guys !! thanks much appreciated !!!
I dont know how to insert the image as photo and cropping,, so I just uploaded one page from questions.

4)
Calculate bond enthalpy for every eqn
Example for R, (410*3) + [(-340)+(-410*3)] =-340
P=193
Q=-244
R=-340
S=410

5)
1/2I2 + 3/2cl2 ----> Icl3
Hence enthalpy for both eqn will be halved
Hence enthaply change of formation of Icl3 = -107 + 19 = -88