Chemistry: Post your doubts here!

[snowbrood]

Chemistry help !, I couldn't find information related to that dicarboxylic acid reacts with little c.H2SO4 to give a cyclic compound, in neither AS level nor A2 Level. It is such a totally weird question.

Question 5 (d) (i)

Could you guys plz help me?

lets see look buddy there are two possible reactions to this
1.conc sulfuric acid will form an alkene but the number of C atoms will remain the same
2. conc sulfuric acid is also used for esterification esterification will increase the number of C atoms wont they.
well the examiner says there is a cyclic compound meaning there will be minimum of 6 C atoms
he didnt provide us with an acid or alcohol ?? well he doesnt had to as X is both alcohol and acid

 

[Jacob Park]

lets see look buddy there are two possible reactions to this
1.conc sulfuric acid will form an alkene but the number of C atoms will remain the same
2. conc sulfuric acid is also used for esterification esterification will increase the number of C atoms wont they.
well the examiner says there is a cyclic compound meaning there will be minimum of 6 C atoms
he didnt provide us with an acid or alcohol ?? well he doesnt had to as X is both alcohol and acid

Just wondering, then why does it form a cyclic compound rather than straight line ester?

 

[snowbrood]

Just wondering, then why does it form a cyclic compound rather than straight line ester?

actually for a straight line ester u need one alcohol plus one carboxyllic acid. here as we take two X each has alcohol carboxyllic acid . alcohol and carboxyllic acid react forming an ester group two ester group isnt that hard see

 

[Vaidik Shah]

What kind of reaction is hydrazine with HCl??

 

[Lady Lyy]

Can anyone please tell me where i can find the marking scheme for chemistry paper 1 5070 ?
Thanks.

 

[Vaidik Shah]

Please help me
What is formed from Reaction of ethanal with propanal

 

[harsh007]

did anybody write chemistry paper 2?

 

[Alice123]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_41.pdf
Q3 dii somebody please help...

 

[6Astarstudent]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_41.pdf
Q3 dii somebody please help...

conversion of indigo (C16H10N2O2) to -> C16H28N2O2
total of 18 H gained, so must be 9H2 in the reactants
ie. full equation something like this C16H10N2O2 + 9H2 -> C16H28N2O2

next we calculate mol of indigo
n(C16H10N2O2)= 2.5 / (12x16 +10 + 2x14 + 2x16) = 2.5/262 = 9.54x10^-3 mol
and we know n(H2) = 9n(C16H10N2O2) from above equation so n(H2) = 9 x 9.54x10^-3 = 0.0859 mol

under room temperature and pressure, 1mol of gas occupies 24dm^3 volume so
V(H2) = 24 x 0.0859 = 2.06 dm^3

 

[Afza Munir]

explain the following:
a) why are most metals strong ,but ionic solids are brittle?
b) why is an alloy of copper and tin stronger than either copper or tin alone?

 

[Alice123]

conversion of indigo (C16H10N2O2) to -> C16H28N2O2
total of 18 H gained, so must be 9H2 in the reactants
ie. full equation something like this C16H10N2O2 + 9H2 -> C16H28N2O2

next we calculate mol of indigo
n(C16H10N2O2)= 2.5 / (12x16 +10 + 2x14 + 2x16) = 2.5/262 = 9.54x10^-3 mol
and we know n(H2) = 9n(C16H10N2O2) from above equation so n(H2) = 9 x 9.54x10^-3 = 0.0859 mol

under room temperature and pressure, 1mol of gas occupies 24dm^3 volume so
V(H2) = 24 x 0.0859 = 2.06 dm^3

thanks...

 

[Alice123]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_43.pdf
Q5c anyone please explain

 

[ikyorince]

Is there anyone appearing As chemistry 9701/22 this oct-nov 2013?? The exam in my country got postponed for some reason and I guess they'll take it after two days. So, if any of you have given this paper or any variant 21 or 23, can u post here the questions u remember? a slight help would be remembered forever. I AM A VERY WEAK STUDENT, plz someone help me

 

[6Astarstudent]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_43.pdf
Q5c anyone please explain

5bi
production of O2
given cathode equation from question: 2H2O(l) + 2e– -> H2(g) + 2OH–(aq), find E value in data booklet = -0.83V
now we find anode equation, we know the reaction was neutral at the start so reactant must be ph7 (H2O) so must be O2 + 4H+ + 4e– ⇌ 2H2O = +1.23V
E = (1.23 – (–0.83)) = 2.06V

5bii
cathode reaction is still the same 2H2O(l) + 2e– H2(g) + 2OH–(aq) -0.83V
anode for production of Cl2 Cl 2 + 2e– -> 2Cl – +1.36V
Eo = (1.36 – (–0.83)) = 2.19V

5ci
Cl2:O2 ratio as [Cl-] increases
we look at the the equation from production of O2 and Cl2
in production of O2, Cl- concentration is not related so there will be no change
in production of cl2, if you increase Cl- concentration equilibrium of Cl 2 + 2e– -> 2Cl – shifts back to the reactants (left) so E value decrease (less positive)

5cii
same as part i, because [Cl-] increase, equilibrium shifts to reactants , E value decrease so more Cl2 is formed
O2 does not change
so Cl2(g) : O2(g) increases

 

[nirajsuroopjet]

hi you all, am searching for chemistry p4 topical past papers for chemistry of live, applications of analytical chemistry and design and material

 

[Jinosupreme]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

 

[KZW]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

(CH3)3CCH2OH will not dehydrate into an alkene. The reason being is that there can't be a double bond formed, as there are already 3 methyl groups on the carbon on the end. Carbon can only form up to 4 bonds, and so the reaction from alcohol to alkene is not possible here.

 

[KZW]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

(CH3)3CCH2OH will not dehydrate into an alkene. The reason being is that there can't be a double bond formed, as there are already 3 methyl groups on the carbon on the end. Carbon can only form up to 4 bonds, and so the reaction from alcohol to alkene is not possible here.

 

[ZaqZainab]

A tiny doubt i just started my AS but i can't understan what Azimuthal means i tried google still don't get it Can anyone help ASAP

 

[MemoryMatrix 21]

What are the exact 2 graphs of heterogenous catalysis??