Chemistry: Post your doubts here!

[nehaoscar]

Can you tell me which paper this is?

Specimen paper 2016

 

[Eugene99]

View attachment 58765
How to find oxidation number on Carbon using the figure??
Metanoia

Since oxygen's oxidation number is taken to be -2
suppose carbon's is x and overall oxidation number of ion as the structure shows is -2. So, here is how we set it up:
( -2x4) + (2x) = -2
-8 + 2x=-2
2x=-2+8
x=+3

 

[My Name]

Since oxygen's oxidation number is taken to be -2
suppose carbon's is x and overall oxidation number of ion as the structure shows is -2. So, here is we set it up:
( -2x4) + (2x) = -2
-8 + 2x=-2
2x=-2+8
x=+3

For the overall wont it be the (-2( + (-2( ?That is we take charge of both the oxygen ions?

 

[Eugene99]

For the overall wont it be the (-2( + (-2( ?That is we take charge of both the oxygen ions?

no...each oxygen ion has -1 charge so for both -1x2 which is -2

 

[nehaoscar]

Since oxygen's oxidation number is taken to be -2
suppose carbon's is x and overall oxidation number of ion as the structure shows is -2. So, here is how we set it up:
( -2x4) + (2x) = -2
-8 + 2x=-2
2x=-2+8
x=+3

Thankyou! Could you help me with these ones too?

View attachment 58763
Please explain how to do this one
Metanoia

View attachment 58764
How to find order wrt H+ ??
I found the others as 1 but idk how to do it for H+
Metanoia

 

[The Sarcastic Retard]

View attachment 58763
Please explain how to do this one
Metanoia

(i) CH3CHO + 2CH3OH <===H+===> CH3CH(OCH3)2 + H2O
At eq.
conc. of CH3CHO = (0.2 - x)
Conc of 2CH3OH = (0.1 - 2x) as 2 moles of it is there so 2x moles will be less.
conc of Acetyl A = x
conc of H2O = x as 1 mole of it is there so x.

 

[Eugene99]

Thankyou! Could you help me with these ones too?

Mr. Retard explained the (a) part and I doubt if I can do the (b) part, maybe I needa revise the equilibrum chapter! is it from there?

 

[nehaoscar]

Mr. Retard explained the (a) part and I doubt if I can do the (b) part, maybe I needa revise the equilibrum chapter! is it from there?

It's from reaction kinetics

 

[nehaoscar]

I don't understand why there will be no change in the beaker with Fe3+/Fe2+
Surely adding SO4- to there will also affect the equilibrium due to the common ion effect...
So why no change??
Metanoia

 

[Eugene99]

It's from reaction kinetics

in fact I haven't covered A2 yet! what I have covered I can answer pretty well

 

[nehaoscar]

in fact I haven't covered A2 yet! what I have covered I can answer pretty well

Haha ok no problem

 

[Catherine_1]

http://cieoandalevelnotes.blogspot.in/2015/05/chemistry-level-paper-5-p5-solved-past.html

Thank you so much!

 

[awesomaholic101]

Thank you so much!

no problem

 

[The Sarcastic Retard]

View attachment 58766
I don't understand why there will be no change in the beaker with Fe3+/Fe2+
Surely adding SO4- to there will also affect the equilibrium due to the common ion effect...
So why no change??
Metanoia

Metanoia

 

[Metanoia]

View attachment 58766
I don't understand why there will be no change in the beaker with Fe3+/Fe2+
Surely adding SO4- to there will also affect the equilibrium due to the common ion effect...
So why no change??
Metanoia

hmm..this question was addressed here.

https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-733#post-942233

 

[Metanoia]

View attachment 58764
How to find order wrt H+ ??
I found the others as 1 but idk how to do it for H+
Metanoia

order with respect to [CH3CHO] is 1
order with respect to [CH3OH] is 1

You would need answers to part a and b to find order with respect with H+, compare any two experiments and also sub in orders with respect to [CH3CHO] and [CH3OH].

e.g
Experiment 1 and 4

 

[Metanoia]

Can anyone please explain the VSEPR (valence shell electron pair repulsion) theory that we are supposed to know for chapter 3 (chemical bonding) in AS Chem? Also, I do not understand the rules. I mean, if a rule states that if there are 4 pairs of electrons (no lone pairs) around the central atom then the molecule is said to be tetrahedral with a bond angle of 109.5 degrees, however, that is not the case with a CO2 molecule which I don't seem to get as to why it is linear and not tetrahedral even though it has 4 pairs of electrons around the Carbon atom. If anyone could explain or direct me to a link online which explains it clearly with all the rules that we are supposed to know to determine the shape that would be really helpful.

Thanks.

Rather than view it in terms of "electron pairs", it is more correct to view it as "electron groups", so there are two electron groups around the carbon atom in CO2.

I did a few videos on molecular shapes, hope they might be useful to clear things up for you.

 

[The Sarcastic Retard]

hmm..this question was addressed here.

https://www.xtremepapers.com/commun...st-your-doubts-here.9859/page-733#post-942233

I dont get it.

 

[The Sarcastic Retard]

Part (ii)

 

[leenz98]

Can someone please explain as many questions as possible from amongst mcq no 12,17,19,20,22,26,28,29 of 9701 MJ 2011 paper 12. Thanks in advance.