Chemistry: Post your doubts here!

[asadalam]

Can anyone show me to how to solve this??

c part?

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9701 - Chemistry/9701_w05_qp_2.pdf
In question 5 part f, shouldn't the aldehyde change into OO-C-R as the reaction of Tollen's reagent woth aldehyde yeilds:
CH3CHO+(Ag(NH3)2)+----> CH3COO- ?? Anyone?

Either is correct in recent paper as i saw in a question both were accepted RCOOH and RCOO- as the product of reaction with tollens.This is an old one so dont worry.

 

[nehaoscar]

Anyone have any last minute notes, tips and predictions for questions/topics that may come up tomorrow?

 

[Mahnoorfatima]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9701 - Chemistry/9701_w08_qp_2.pdf
How do I draw the hess cycle in Question 2 part cii?

 

[The Sarcastic Retard]

Anyone have any last minute notes, tips and predictions for questions/topics that may come up tomorrow?

Haha.. Just stay relaxed, dont be in hurry, but make sure you finish your paper in time.
Prediction : Everything is coming.

 

[The Sarcastic Retard]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9701 - Chemistry/9701_w08_qp_2.pdf
How do I draw the hess cycle in Question 2 part cii?

Like this :¬

 

[nehaoscar]

Haha.. Just stay relaxed, dont be in hurry, but make sure you finish your paper in time.
Prediction : Everything is coming.

Haha Chemical periodicity is my worst nightmare! (So is all of chem tbh )
And Maths P1 tomorrow too... ughh
Thanks though!

 

[The Sarcastic Retard]

Haha Chemical periodicity is my worst nightmare! (So is all of chem tbh )
And Maths P1 tomorrow too... ughh
Thanks though!

All the best ^_^
For me physical and inorganic part is and organic is

 

[nehaoscar]

All the best ^_^
For me physical and inorganic part is and organic is

Thanks! Haha for me organic is ok ok ... But enthalpy and equilibrium are EPIC
Good luck!

 

[The Sarcastic Retard]

Haha Chemical periodicity is my worst nightmare! (So is all of chem tbh )
And Maths P1 tomorrow too... ughh
Thanks though!

Thanks.

 

[The Sarcastic Retard]

Can anyone show me to how to solve this??

Assuming ur doubt to be
bii)
Its just tricky. We have to reverse the process. Its the same way we use to do to find Ar, we have Ar and now we have to find relative isotopic abundance.
Let percentage abundance of 80.92Br be x and of 78.92 be 100-x
Ar = 79.2
79.2 = [(80.92x) + (78.92(100-x)]/100
x = 49 = relative isotopic abundance of 81Br
100-49 = 51 = relative isotopic abundance of 79Br

c)
This is also tricky, we have to reverse the process.
ABr3 has 1:3 ratio
A : 4.31 / Ar = 1
Br : 95.69/79.9 = 3

A : Br
1 : 3
4.31/Ar : 95.69/(79.9*3)
Ar = 4.3/(95.69/239.7) = 10.79

 

[a_wiserME!!]

how will you define equilibrium constant??

 

[The Sarcastic Retard]

how will you define equilibrium constant??

http://chemistry.about.com/od/chemistryglossary/g/Equilibrium-Constant-Definition.htm

 

[nehaoscar]

What are observations on all the reactions of period 3 elements with H2O, Cl and any other reagent in the syllabus?

 

[Mahnoorfatima]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9701 - Chemistry/9701_s08_qp_2.pdf
For question 5, part cii, can we write the structural formula of the p.alcohol as HOCH2CH2OH? In MS its written as HOH2CCHO? What's the diff? Will my ans be considered wrong?

 

[Mahnoorfatima]

What are observations on all the reactions of period 3 elements with H2O, Cl and any other reagent in the syllabus?

Okay so only 3 elements in P3 react with H2O i.e Na,Mg and Cl. Na would float on H2O,and catch fire. An exotherminc reaction will occur. Na+H20- NaOH+H2 Ph is 14
Mg's reaction will be slow, bubbles of H2 will form after a long time. But it's reaction with steam will be faster. PH is 9
Cl2 will react with H2O to prduce HClO and HCl. Ph is 2-6 . That's just for H2O

 

[mehria]

Best organic notes please?
mehria

i'll post it tonight inshAllah.. but those notes only contain reactions...nthng else

 

[Studydayandnight]

Assuming ur doubt to be
bii)
Its just tricky. We have to reverse the process. Its the same way we use to do to find Ar, we have Ar and now we have to find relative isotopic abundance.
Let percentage abundance of 80.92Br be x and of 78.92 be 100-x
Ar = 79.2
79.2 = [(80.92x) + (78.92(100-x)]/100
x = 49 = relative isotopic abundance of 81Br
100-49 = 51 = relative isotopic abundance of 79Br

c)
This is also tricky, we have to reverse the process.
ABr3 has 1:3 ratio
A : 4.31 / Ar = 1
Br : 95.69/79.9 = 3

A : Br
1 : 3
4.31/Ar : 95.69/(79.9*3)
Ar = 4.3/(95.69/239.7) = 10.79

Thanks for replying!

 

[Studydayandnight]

I have a question in organic chemistry, what is the role of conct. H2SO4? I know that it forms a double bond and stuff, but what else does it do?

 

[Dark Destination]

I have a question in organic chemistry, what is the role of conct. H2SO4? I know that it forms a double bond and stuff, but what else does it do?

Acts as a catalyst and dehydrating agent.

 

[nehaoscar]

http://studyguide.pk/Past Papers/CIE/International A And AS Level/9701 - Chemistry/9701_s08_qp_2.pdf
For question 5, part cii, can we write the structural formula of the p.alcohol as HOCH2CH2OH? In MS its written as HOH2CCHO? What's the diff? Will my ans be considered wrong?

better just write the hydrogens next to the OH like HOH2CCH2OH... i think they would mark it right cause it's correct but better stick to the order they use it