Chemistry: Post your doubts here!

[sumeru]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s13_qp_42.pdf

Anyone generous to help
Q2 part b

 

[sumeru]

Can you elaborate the point ? or compare it with the other two ? For cathode > more positive E vlaue will go to cathode and no doubt in that ..
What about anode?

Ok....for cathode the two candidates are Mg2+ and H+ and according to E values ...H+ has more tendency to get reduced ....and for anode....at anode,oxidation occurs...so,the candidates are OH- and Br-....now, for cathode, if E values is positive, than that elements will get reduced.....and for anode, those elements having negative E vales will get oxidised.........

 

[periyasamy]

Hi guys,want to ask smthg.
How do i see which is identical.All seems same for me.Haha
The answer is j

 

[periyasamy]

Hei guys.Can anyone help me with this terribly hard question from may june 13 paper.Thank u.
My doubts r the last 3 reaction.
a)how can the 6th rxn be a ligand exchange
b)how can the last rxn show a ligand exchange n no acid base.Isnt there suppose to be acid base when got prescence of water as product.Thanks a lot.....

 

[sitooon]

Ok....for cathode the two candidates are Mg2+ and H+ and according to E values ...H+ has more tendency to get reduced ....and for anode....at anode,oxidation occurs...so,the candidates are OH- and Br-....now, for cathode, if E values is positive, than that elements will get reduced.....and for anode, those elements having negative E vales will get oxidised.........

02+2H2O+4e=4OH- E value is +0.40V
Br2+2e=2Br E value is + 1.07V

OH has lower ( more negative ) Evalue , so it will be at anode ???????

 

[sumeru]

OH- oxidises to give O2........you must be knowing that metals goes to cathode and non metal to anode......and at anode, oxidation takes place....and according to our E values, less positive have more tendency to get oxidised...

 

[sitooon]

OH- oxidises to give O2........you must be knowing that metals goes to cathode and non metal to anode......and at anode, oxidation takes place....and according to our E values, less positive have more tendency to get oxidised...

My friend you said it , " less positive have more tendency to get oxidised... "
So its oxygen which will be at anode ( less positive E value ) NOT Br ..

 

[itallion stallion]

in 4e u can join the amino acids in any order but there should be 3 amino acids present and 2 peptide bonds present
hmmm we use only dilute HNO3 when theres reaction with a phenol and H2SO4 and HNO3 when theres benzene or whtever got it?

Thanks a lot!what if there is a methyl group at position 1 and OH at position 4 in benzene ring what will I use for nitration?
Reminder for the alpha helix structure( plz a simpler one)
Thanks

 

[itallion stallion]

Sitoon can u plz help me with May June 2006 paper4 q4 diii.thanks aloot!

 

[Haya Ahmed]

please some one help me http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s06_qp_1.pdf

Q23 , Q20 , Q15 , Q17 , Q11 , Q5 , Q6 , Q3 ... answer as much as you can .. so that I don't disturb you and inbox me if required thanks ^_^

 

[itallion stallion]

the first one is complicated but the second one has to be drawn in the exam n its quite simple i belief wht do u think?

Thanks! Yeah it is simple (a bit)
Thanks again!

 

[sumeru]

My friend you said it , " less positive have more tendency to get oxidised... "
So its oxygen which will be at anode ( less positive E value ) NOT Br ..

Ahhhh...what did i do up there......sorry....i,myself got pretty confused ....let me think....

 

[Haya Ahmed]

Please Help me !!!

 

[Haya Ahmed]

Help me please !

 

[goodluckayesha]

Thanks! Yeah it is simple (a bit)
Thanks again!

cudnt expect to be any more simpler afterall we r doing A2 not KG2

 

[goodluckayesha]

Thanks a lot!what if there is a methyl group at position 1 and OH at position 4 in benzene ring what will I use for nitration?
Reminder for the alpha helix structure( plz a simpler one)
Thanks

no matter wht else is present as far as ik if OH is present then for nitration u use dilute HNO3
yh i posted tht n u saw it also

 

[sitooon]

Please Help me !!!

Hydrogen bond is between hydrogen and highly electronegative ion ( N , O , F ) .. so B only has this H --- N in ammonia

 

[sitooon]

Help me please !

Its , Cl2 + KI ---> KCl + I2
Oxidation state of element is zero .. and in KI oxidation state of iodine is -1 ... therefore it changes from -1 to 0 ( increase in oxidation state ) which is oxidation

 

[Haya Ahmed]

Its , Cl2 + KI ---> KCl + I2
Oxidation state of element is zero .. and in KI oxidation state of iodine is -1 ... therefore it changes from -1 to 0 ( increase in oxidation state ) which is oxidation

Thanks and If you don't matter can you explain this one too !

 

[sumeru]

My friend you said it , " less positive have more tendency to get oxidised... "
So its oxygen which will be at anode ( less positive E value ) NOT Br ..

My friend, i tried doing it using the E values......but, i did not match with what we have actually studied...but on our coursebook, an list of increasing ease of oxidation of elements are given...see that...it will help you