GT for Chemistry paper 22 AS.

[littlecloud11]

the problem is that i draw whole structures in every part evn in q.5 i dunt know whether we had to draw them or chow just the structural formula.
though all the structures were correct t i made the whole structures labelling every bond. in q.5 did u draw the whole structue. the last 1 was triol when we oxidised cmpound G, did u draw whole structure?

they'll accept displayed formula for all the structures in question five. I've seen it in past mark schemes.

 

[Pals_1010]

''HO2CCH2CH(OH)CO2H + conc. H2SO4----->HO2CCH=CHCO2H''

I wrote the product as HO2CCHCHCO2H.... Is that acceptable?

 

[good man12]

Q3 answers:

HO2CCH2CH(OH)CO2H + CH3OH----------->CH3O2CCH2CH(OH)CO2CH3
HO2CCH2CH(OH)CO2H + CH3CO2H-------->HO2CCH2CH(CO2H)O2CCH3
HO2CCH2CH(OH)CO2H + conc. H2SO4----->HO2CCH=CHCO2H

HO2CCH=CHCO2H + hot conc. KMnO4----->HO2CCHO
HO2CCH=CHCO2H + cold dil. KMnO4------->HO2CCH(OH)CH(OH)CO2H
HO2CCH=CHCO2H + steam/H3PO4--------->I did this one wrong =[.. but it should be HO2CCH2CH(OH)CO2H

in hot conc it should be HOOCCOOH,
and for second ester it is general principal to put structure of the carboxylic acid befor the alcohol in the ester

 

[angelicsuccubus]

there was no chlorine mentioned in the question.
only which element burns with a colored flame, and the possible answers were. sodium (yellow), phosphorous (blue), sulfur (yellow)

no I think they did mention which element in period 3 burns with a coloured flame in chlorine... but I wrote sodium (didn't know the answer)

 

[angelicsuccubus]

''HO2CCH2CH(OH)CO2H + conc. H2SO4----->HO2CCH=CHCO2H''

I wrote the product as HO2CCHCHCO2H.... Is that acceptable?

I think so, yeah

 

[littlecloud11]

Yes increasing the temp would lower the equilibrium yeild as the forward reaction was exothermic

lol. the answer was -129.

and you won't get marks if you used le chatelier's principal. the equation was NOT an equilibrium reaction.

 

[angelicsuccubus]

in hot conc it should be HOOCCOOH,
and for second ester it is general principal to put structure of the carboxylic acid befor the alcohol in the ester

no, with hot conc MnO4 ions.. the double bond breaks and you get two compounds, they take either answer.. but what you made. .I don't see how that's possible...

and oh okay, for the genereal principal, didn't know that.

 

[xxfarhaxx]

I hadn't notice it was SKELETAL formula that was asked for the cis-trans isomer(silly mistake I know) but I saw it like when 5 mins was left, and I hastily drew these. Do you think I'll get my marks?

i drew da xact thng!!! its half skeletal..will v gt mrks???

 

[angelicsuccubus]

they'll accept displayed formula for all the structures in question five. I've seen it in past mark schemes.

q4.. not 5

 

[good man12]

no, with hot conc MnO4 ions.. the double bond breaks and you get two compounds, they take either answer.. but what you made. .I don't see how that's possible...

and oh okay, for the genereal principal, didn't know that.

ur rite...the double bond breaks, but from what i learned in my course is that the "CHO" which forms doesnt exist as the hot mno4 ions immediately oxidise it to COOH and in many past papers ive done it is always a COOH when hot con mno4 is used with alkene RCH= group....

 

[littlecloud11]

no I think they did mention which element in period 3 burns with a coloured flame in chlorine... but I wrote sodium (didn't know the answer)

I'm 100% positive abt this. Mention of chlorine only came in the next part and that was with Al.

 

[Pals_1010]

i drew da xact thng!!! its half skeletal..will v gt mrks???

Apparently we'll get at least 1 mark out of the 2

 

[angelicsuccubus]

ur rite...the double bond breaks, but from what i learned in my course is that the "CHO" which forms doesnt exist as the hot mno4 ions immediately oxidise it to COOH and in many past papers ive done it is always a COOH when hot con mno4 is used with alkene RCH= group....

ack okay i donno

 

[00tanveer]

Well, I don't remember any trio being formed! Are you sure it was a triol? Which question are you talking about? It would help if you posted the whole question as it was.

 

[angelicsuccubus]

I'm 100% positive abt this. Mention of chlorine only came in the next part and that was with Al.

I wrote down the questions on a piece of paper later and I have it as burns in chlorine but I hope youre right

 

[00tanveer]

You just got trolled by yourself dude!!! You misread the question. Sorry man, but the reatction concerned was the FORMATION OF METHANOL from CO AND H2. Hope you got it.

 

[littlecloud11]

3 marks = optical.......3=skeletal ...3= emperical.....3= reactions.....1= esters use.....6= chart or reaction....total =16

you mixed up question 2 and 3 i think.

 

[00tanveer]

Oh sorry my bad!!! I've made a silly maistake here. I'm correcting it.

 

[littlecloud11]

Q1
i wrote sodium for the colored flame with chlorine.. not sure
2Al(s) + 3Cl2(g)--> AlCl3(s)
when this reaction occurs, the pale yellow color of the gas disappears and a white solid is formed
Argon doesn't react as it is in a stable elemental state because of its full octet.
Sodium dissolves pH 7
Aluminum dissolves pH 6-- ?..
Silicon reacts pH 3
Reaction is redox/disproportionation
Sulfur- 2 lone pairs
Nitrogen- 1 lone pair
Bond A is smaller due to the presence of 2 lone pairs compared to just 1, thus repelling bond pairs more.

Q2
Ch3OH(l)+3/2O2(g) = CO2(g) + 2H2O(l)
enthalpy change is -129 kJ/mol
increase in pressure increases rate of formation due to increased interaction/collisions between reactant molecules
increase in temp. increases rate of formation due to more particles having energy greater than Ea
presence of catalyst increases rate of formation as it lowers Ea
_______The reaction was an irreversible reaction, so the concept of equilibrium shifts cannot be incorporated________

Q3
I don't remember the exact structure of the compound but
to the left, an ester with the tail -CO2H groups were formed
to the right, an ester with the middle -OH group was formed
straight down, an alkene was formed with the elimination of the middle -OH group and a hydrogen from one of the neighboring C's
alkene + cool, dilute KMnO4 gave you a product with the double bond removed and a diol
alkene + hot, conc. KMnO4 gives you something i'm not sure of!
NOTE--- I have just talked about the parts of the compounds that have changed, everything else is meant to be the same
I cannot recall the reaction we had to write the types of...
the optical isomer was easy
My cis-trans isomers looked the same as Pal_1010's..-- Am I right?

For the fourth que,
Na--- -CO2H and -OH
K2Cr2O7 & heat---- -OH and -CHO
NaHCO3--- -CO2H-- (I remember cuz its a test :O)
i got the functional group as -oh -- alcohol
moles of hydrogen atoms as 6.67x10^-3
proved the presence of 2 -OH groups by showing the ration of R-OH
and the presence of a ketone group.
The structure of G was CH2(OH)C=OCH2(OH), drawn of course!
the empirical formula was C6H8O7.... But I wrote C7H9O8.. if I have made a mistake in multiplying the correct base ratio of CHO- C1H1.3O1.17 with a factor, do you think I can get at least 2/3 marks?.. :/



Guys, Do correct me where necessary..

In the first question the pH of Al chloride was in the range 1-3
and the reaction was hydrolysis.

 

[00tanveer]

I've corrected the diagram. Go check it again. Thank you.