Chemistry P4| A2 only

[BURHAN UL HAQ]

Hi i have a past paper question:
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s08_qp_4.pdf
Please see page 7 of it..and see the last part ....I cant understand this
In the previous part delta H for M=Si is -474kj/mol and for next part M=Sn delta H is=-386 kj/mol..
Now as we know that Sn is more stable in +4 Oxidation state and Pb is more stable in +2 oxidation state...then how do results in calculation support this fact???
It is contradictory for me , becauase stability of a compound is associated with its enthalpy change..More exothermic is the formation of a compound..more stable it is....but here formation of SnCl4 is less exothermic (-386kJ/mol) and formation of PbCl4 is more exothermic....Pls see. and help me!

 

[angelgirl:)]

I will show you tomorrow!

lol ok...but i got the intermediate 1...

 

[hassam]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_y07_sp_4.pdf
Q2 C (ii)
++++
Give two reasons why lime is used in agriculture.

 

[RGBM211]

mmm why is there only three arrows shouldnt it be like this
and you havent explained me the rest of the part

 

[smzimran]

mmm why is there only three arrows shouldnt it be like this
and you havent explained me the rest of the part View attachment 10395

Yes, maybe depending on how many eletrons are there in the d orbital!

I posted the image of an element having 3 electrons in its d orbital so thats why

 

[RGBM211]

Yes, maybe depending on how many eletrons are there in the d orbital!

I posted the image of an element having 3 electrons in its d orbital so thats why

so what is the right answer ?
and please explian the rest of the question

 

[Zishi]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_y07_sp_4.pdf
Q2 C (ii)
++++
Give two reasons why lime is used in agriculture.

To neutralise acid in soil and to improve soil quality by precipitating clays.

 

[smzimran]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_41.pdf
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_ms_41.pdf

can someone explain 3b)

In diagram, you do not have to show electrons!
Just show the orbitals, thats it!

Complexes are coloured because when an electron in lower orbital moves to high orbital, it needs energy!
This energy it gets as it absorbs a photon of energy E = hf
As it absorbs some frequencies of light and reflects the rest, it is coloured!

The 'E' in the formula E =hf is dependent on the ligand present.
So if ligands are changed, 'E' changes hence different frequency lights are absorbed and reflected, so colour changes!

 

[leadingguy]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_43.pdf
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_ms_43.pdf

QUESTION 5 C i) can any one explain this?????

 

[histephenson007]

In diagram, you do not have to show electrons!
Just show the orbitals, thats it!

Complexes are coloured because when an electron in lower orbital moves to high orbital, it needs energy!
This energy it gets as it absorbs a photon of energy E = hf
As it absorbs some frequencies of light and reflects the rest, it is coloured!

The 'E' in the formula E =hf is dependent on the ligand present.
So if ligands are changed, 'E' changes hence different frequency lights are absorbed and reflected, so colour changes!

Isn't this quantum physics?? :S Y is it here!!! ?!

 

[smzimran]

Isn't this quantum physics?? :S Y is it here!!! ?!

Yes it is similar to that
It is here but not that much detailed knowledge is needed as needed in Physics!

 

[musa Khan]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_41.pdf

question number 2 ai , how do you find out the order for H+ ?

 

[smzimran]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_41.pdf

question number 2 ai , how do you find out the order for H+ ?

I've solved this one before!
Here:
Click here

 

[musa Khan]

can you solve again? that thread is toooo long!

 

[smzimran]

can you solve again? that thread is toooo long!

Click on the link!
It will take you directly to the answer!

 

[musa Khan]

oh okay haha sorry! and thank you!

 

[RGBM211]

In diagram, you do not have to show electrons!
Just show the orbitals, thats it!

Complexes are coloured because when an electron in lower orbital moves to high orbital, it needs energy!
This energy it gets as it absorbs a photon of energy E = hf
As it absorbs some frequencies of light and reflects the rest, it is coloured!

The 'E' in the formula E =hf is dependent on the ligand present.
So if ligands are changed, 'E' changes hence different frequency lights are absorbed and reflected, so colour changes!

you just quoted the same thing like the markscheme :/ oh well nvm

 

[smzimran]

you just quoted the same thing like the markscheme :/ oh well nvm

Bhai I didnt even open the mark scheme!!!

RGBM211:
Yaar i cannot write the whole lecture down, will take a lot of time,

I think your doubts will be cleared after reading this:
http://www.chemguide.co.uk/inorganic/complexions/colour.html#top

 

[hassam]

To neutralise acid in soil and to improve soil quality by precipitating clays.

i dint understand tyhe second point ....zsihi thats why i askked

 

[sweetyrox]

hiii everyone..i was facing problems in section B ques...when they ask about PVC...plastic..glass etc :S:S info on all this isnt given in the application booklet..and these questions are frequesntly asked nowadays..sooo does anyone know what we are supposed to know concerning this or does anyone have some resourse??