Chemistry: Post your doubts here!

[chocolate_girl]

The rcocl reaction with rnh2,,,,iS SUCH THAT the rcocl act as an acid(rcooh)...The product will actually belike ester,----->RCONH2R'..

But this way wont nitrogen bond with four atoms

 

[A star]

But this way wont nitrogen bond with four atoms

yes nitrogen can bond with four atoms if the fourth is a dative bond and i guess that compound is a amide

 

[daredevil]

I ll rephrase it

What is the compound R'CONH2 called?
And as u said there is a reaction RCOCl+R'NH2 and product is R'CONH2 the R here is the R of R'NH2 so where did the R for RCOCl go?

Ummm there was an error in that equationn....


RCOCl + R'NH2 --> RCONHR' + HCl

 

[chocolate_girl]

1. understand, in simple terms, the concept of electronegativity
   and apply it to explain the properties of molecules such as bond polarity (3h), the dipole moments of molecules (3j), the behaviour of oxides with water (3.1j) and the acidities of chlorine-substituted ethanoic acids (10.6c)
   
   Please explain me the last chlorine substituted ethanoic acid part

 

[chocolate_girl]

yes nitrogen can bond with four atoms if the fourth is a dative bond and i guess that compound is a amide

Thankyou im really greatful

 

[chocolate_girl]

Ummm there was an error in that equationn....


RCOCl + R'NH2 --> RCONHR' + HCl

Thanks for ur time

 

[asd]

Question explaination needed :-/

I didnt get how they calculated it

Umm did you get your answer yet?
well, not in a mood to go through all those 8 pages.
Khair, look how theyre changing the concentrations of the reactants, and how the initial rate of the reaction changes. Work them out in fractions; change in conc of reactant A= 1.6/1.1= 1.45 which equals the change in initial rate, 2.3/1.6. Apparently, changing the concentration of reactant B has no effect on the rate, since all the effect is only coming from the reactant A alone. So, change in reactant A is proportional to change in initial rate. therefore, first order with respect to reactant A, and 0 w.r.t B.

 

[asd]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_42.pdf

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_ms_42.pdf

Q 3 c... y is another compound made?? is it like instead of C a cmpound D is made or what??

Both compounds are being formed at the same time. And no, D is not being made in place of C. However, in my opinion C is the preferential product of the reaction since production of D has a relatively longer route.
And for why D is being made, compound B dissociates in the aq solution giving the organic anion, and the Na+ cation. The negative charge on the Oxygen atom travels to the Oxygen atom at the bottom (Double bond b/w 2 carbon atoms on the right side of the molecule acts a bridge in extending the pi-bonding system). Oxygen at the bottom now acts a nucleophile and attacks on the positive Carbon atom on the enthanoyl chloride. Another possibility in my opinion could be that the electrons travel to the oxygen at the top and this could be another potential nucleophile allowing CH3CO+ to attach to this oxygen.

 

[Hassan Ali Abid]

Who has an idea of the likely practical questions in paper 3 for 2014

Which variant ???

 

[NinjaInPyjamas]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_22.pdf

q3 please help!
I have difficulty deriving the formula...is there a way to understand easier?

Thanks in advance!

 

[Hassan Ali Abid]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_22.pdf

q3 please help!
I have difficulty deriving the formula...is there a way to understand easier?

Thanks in advance!

The simplest way is to open the given structure so that u can have a better of idea and then u can use ur knowledge+ understanding to solve such type of questions ...
eg in this question when u open the given compound u can see there are 2 acid groups and one alcohol group ...
to make the structure of A ..u have to recall the reaction of alcohol with acid ....simply 2 ester linkage will be formed in this ..
for making B u see now the alcohol group in compound will react ethanoic acid ..
For making C ...remove the water ( by removing OH and H ) and alkene will form ..
In E...its the reaction with water so again add water in it ....
For F ...its a cold dil reaction of alkene so 2 -OH groups will be added in it ..
In D...as its a reaction with hot .conc. so two products will be formed in it .
If u still didnt get it then i'll draw the structures of all these..okay ..

 

[NinjaInPyjamas]

The simplest way is to open the given structure so that u can have a better of idea and then u can use ur knowledge+ understanding to solve such type of questions ...
eg in this question when u open the given compound u can see there are 2 acid groups and one alcohol group ...
to make the structure of A ..u have to recall the reaction of alcohol with acid ....simply 2 ester linkage will be formed in this ..
for making B u see now the alcohol group in compound will react ethanoic acid ..
For making C ...remove the water ( by removing OH and H ) and alkene will form ..
In E...its the reaction with water so again add water in it ....
For F ...its a cold dil reaction of alkene so 2 -OH groups will be added in it ..
In D...as its a reaction with hot .conc. so two products will be formed in it .
If u still didnt get it then i'll draw the structures of all these..okay ..

thank you so much that was soo helpful! if you don't mind can you please draw organic chemistry is difficult for me
also can you please help with (b) and (d) please
thaanxxx

 

[Hassan Ali Abid]

thank you so much that was soo helpful! if you don't mind can you please draw organic chemistry is difficult for me
also can you please help with (b) and (d) please
thaanxxx

 

[Hassan Ali Abid]

NinjaInPyjamas

 

[chocolate_girl]

1. understand, in simple terms, the concept of electronegativity
   and apply it to explain the properties of molecules such as bond polarity (3h), the dipole moments of molecules (3j), the behaviour of oxides with water (3.1j) and the acidities of chlorine-substituted ethanoic acids (10.6c)
   
   Please explain me the last chlorine substituted ethanoic acid part someone

 

[sidbloom1995]

help plzz

9701.mj.06 q, 25
9701.on.06 q,37,3
9701.mj.01 q 34,26,
9701.on.07 q 33,37,4
9701.mj.08 q 27 ,
9701.on.09 ( varient 11) 28,24,21
9701.on.10(varient 12) 39,27,13
9791.0n.10 (varient 11) q 38 ( what product will form if tollen reagent react with it ),35,29
9701.mj.10 (varient 11) q 12,
9701.mj.11(varient 12) q 38,29,28,24,11,
*9701.mj.11(varient 11) q 36,27,34,26,16
9701.on.11.(varient 12) q 9
9701.on.11 (varient 11) q 27,29,21,
9701.mj.12, (varient 12) q 24,23
9701.mj.12 (varient 11) q 29,23,22,9,
9701.on.12 (varient 11) q 26,

m/j 2011 v.12
Q12 answer is C check the pics for explanation
Q 24 answer is C the answer is in pics

 

[TheStallion-Reborn]

Can someone please tell me what are 'dipole forces'

 

[chocolate_girl]

Can someone please tell me what are 'dipole forces'

Those forces that exist between dipoles, a type of molecular force
e.g. H--Cl molecule Cl gets partial negative charge and H gets partial positive charge hence H(partial positive) of one HCl is attracted towards Cl(partial negative) of the other HCl molecule

 

[Namehere]

anyone knows where i can find winter 2013 chemistry examiners report?

 

[sidbloom1995]

help plzz

9701.mj.06 q, 25
9701.on.06 q,37,3
9701.mj.01 q 34,26,
9701.on.07 q 33,37,4
9701.mj.08 q 27 ,
9701.on.09 ( varient 11) 28,24,21
9701.on.10(varient 12) 39,27,13
9791.0n.10 (varient 11) q 38 ( what product will form if tollen reagent react with it ),35,29
9701.mj.10 (varient 11) q 12,
9701.mj.11(varient 12) q 38,29,28,24,11,
*9701.mj.11(varient 11) q 36,27,34,26,16
9701.on.11.(varient 12) q 9
9701.on.11 (varient 11) q 27,29,21,
9701.mj.12, (varient 12) q 24,23
9701.mj.12 (varient 11) q 29,23,22,9,
9701.on.12 (varient 11) q 26,

Q28. the general equation for empirical formula (e.f) and molecular formula (m.f) is
(m.f) = n(e.f)
where n is a whole number
we have the emperical formula of our acid formed as
C4H8O2
form this we can tell the minimum number of O can be only one and that will only be if we divide it by 2
so [C4H8O2]]/2 = C2H4O
thus this is our answer, C

Q29. im sorry i dont know this one!

Q37. A
we can react C2H4 with H2 at 200*C over the Ni catalyst to get CH3CH3
we can simply polymerize CH2=CH2
we can simply react CH2=CH2 with KMnO4 to get (OH)HC-CH(OH)
so all of them react in a single step to form the given product!

Q38. D
well in this one to be honest i didnt see the 3 choice as the 2 was wrong so the answer is D, only 1
2 is wrong because when we oxidise an alcohol the final product is -CO2H and since we already have a -CO2H group attached to the chiral C* we will not get a C*

m/j 2011 v.11
Q16. this answer is something im not sure of or i dont have any book evidence but it is the logic i used to get my answer so i could be wrong
definition of oxidation is loss of electron, loss of H+
a stronger oxidizing agent will be one that does not donate an H+ to the [Cl-] and [I-] solutions
with H2PO4 white acidic gas was formed, being HCl
were as with H2SO4, with iodine, purple fumes of gas were formed, being I2, meaning [I-] did not receive a H+ and thus was more strongly oxidized then with H2PO4

Q26. im sorry i dont know this one's explanation

Q27. D sodium ethanoate is simply CH3COO-Na+
so look for the ester which form CH3COOH on hydrolysis,
in an ester the C with C=O and the rest of the chain behind it belongs to the acid!
only in D does our chain matches the formula CH3COOH
so D is ou answer!

Q34. NaCl is a salt and cannot give an alkaline solution on dissolving so it is wrong
MgCl2 is slightly hydrolysed by water so it is slightly acidi
AlCl3 is readily hydrolysed and give HCl which is acidic
thus the answer is B

Q36. D
because 2 is wrong, it does not react readily with H2 gas