Chemistry: Post your doubts here!

[Aarjit]

OH. so they want us to memorize the spectrum..that sounds weird. but anyway thanks

I know.. but we have to learn it in quantum physics too [continuos and line spectra].

This will give you a rough estimate:
V I B G Y O R
400 - 700 nm

 

[smartangel]

I know.. but we have to learn it in quantum physics too [continuos and line spectra].

This will give you are rough estimate:
V I B G Y O R
400 - 700 nm

thanks..plz see if you can help me out with this one..
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_41.pdf
Q2a..how is it 1st order with respect to H+..im getting zero :s

 

[Student12]

Does anyone have notes for chemistry AS practicals?

 

[AhsanAadil]

I am expecting 33 in p12, 47 in p22 and 21 in p33. What grade should I expect?

 

[lavanyamane]

oh really ? i took a lot of time to draw the graphs !!!

Graphs? Which paper and variant are we talking about?

 

[princesskt]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s08_qp_4.pdf
tell me q1 a(ii) plz
E=RED-OXI
SHOULDN'T IT BE 1.36-.77

 

[smartangel]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_qp_43.pdf
Q3c..plz tell me how do we dedude the products??

 

[princesskt]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_43.pdf
Q3c..plz tell me how do we dedude the products??

look at the E0 values from booklet the more positive E0 cation discharge at cathode ...............

 

[princesskt]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_4.pdf
tell me q1 a(ii) plz
E=RED-OXI
SHOULDN'T IT BE 1.36-.77

SOMEONE PLZ ANS MY QUESTION.........

 

[smartangel]

look at the E0 values from booklet the more positive E0 cation discharge at cathode ...............

umm so what abt fluorine..its E0 value isnt given in the data booklet.

 

[Romeo10]

Pleaseeeeeee guys can anyone tell me how do u balanceeee the equationnnn in Number 5 in N07 paper 4 pleaseeee help guysssss i just cant balance the equation

 

[mr_perfect]

The degenerate d-orbitals split because of the existent repulsion between the electrons. This helps to form transition-metal-complexes. While forming a complex with a ligand the d-orbitals interact with the surrounding electron cloud, causing it to become non-degenerate (variable energies). This causes photons to be absorbed by the electrons (which then undergo state transitions) to emit radiations with corresponding frequencies (f) to the energy (E) of the photons [where E=hf].

P.S. Electrons in d-orbitals are repelled from the electrons in the ligands, based on electrostatic interactions. This causes two of the d-orbitals (dz2 & dx2-y2) [which have a stronger (repulsive) interaction with the ligand] to be at higher energy than the other three (dxy, dyz, dxz).

u say electrons absorb photon. where exactly do theese photons cum from ? and where does the radiation they emit go to ? . thnx for the knowledge btw

 

[Aarjit]

u say electrons absorb photon. where exactly do theese photons cum from ? and where does the radiation they emit go to ? . thnx for the knowledge btw

Good questions. Allow me to answer them in bullets:

• Photons can come from electron transitions or almost any source of LIGHT;
• Electrons absorb the energy from photons and get promoted to discrete higher energy levels (this is also referred to as adsorption, but wanted to keep the rudiments simple);
• The radiation/photons (ref. wave-particle duality) can then be used to excite other atoms in their ground states, or simply are visualized by our eyes (i.e. if their wavelengths happen to fall in the visible-light spectrum).

I hope that adequately clarifies your doubts.
You surely are pedantic, mr_perfect.*

*no pun intended

 

[mr_perfect]

look, for finding heat of formation when enthalpy changes of combustion are given, the formula to use is pretty simple:
heat of combustion of reactant elements - heat of combustion of product

so if u substitute the values given u'll get the answer like this:

2(-393.7)+ 2(285.9) - (-1411) = +51.8 KJ/mol

xcuse me oldfashionedgirl cud u change your profile pic please . tnx . it is very disturbing .

 

[optimistic]

Can someone please help me with Q3a part 1 and 2! plzzzz.....
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_43.pdf

 

[mr_perfect]

tell me this. in group 4 tetrachlorides down the group the bond length increases right? that means bond strength increases right ? so isn't boiling piont supposed to LINEARLY increase down the group ? WHY DOES BOILING POINT NONLINEARLY DECREASE DOWN THE GROUP ????

 

[hmlahori]

Does anyone have notes on AS practical skills (paper 3) do please post them! my practical is tomorrow........

 

[iKhaled]

Whats a D in paper 3?

 

[saudha]

http://www.chemguide.co.uk/organicprops/alkenes/kmno4.html

pls some one tell me at the end of this page there is a question in this summary ....... related to this:
saudha said: ↑

how do u get a ketone and a carbon dioxide in addition to 2 methyl propane...with hot concentrated KMNO4​

Amy farvin said: ↑

i too dont get it,to explain u.. if anyone knowz plz help us... ​

​

 

[donor]

http://www.chemguide.co.uk/organicprops/alkenes/kmno4.html​

​

pls some one tell me at the end of this page there is a question in this summary ....... related to this:​

saudha said: ↑​

​

how do u get a ketone and a carbon dioxide in addition to 2 methyl propane...with hot concentrated KMNO4​

​

Amy farvin said: ↑​

​

i too dont get it,to explain u.. if anyone knowz plz help us... ​

A CH2 with a double bond always give carbon dioxide and water.
If there are two alkyl groups attached to the double boded carbon atom it will give a Ketone
so 2 methyl propene will give propanone, carbondioxide and water as product with hot conc. KMnO4