[otrivine]

(Original post by mathsclown)
My brain is a bit rusty so not sure if I read your answer correctly, seems right
O=C=O is symmetrical and so the dipoles cancel
C=O is polar because the oxygen is more electronegative, as it has more protons and so attracts the electrons more strongly, so leads to C becoming delta+ and O delta-

Polarity depends on the shape of the molecule AND the molecules present, symmetry leads to dipoles cancelling and the resulting molecule will be non-polar covalent EG. Water is polar becomes it doesnt have a symmetrical gemoetry, it is a bent molecule

no i made a mistake .
Describe margarine production

[mathsclown]

(Original post by otrivine)
no i made a mistake .
Describe margarine production

This is hydrogenation or reduction, it requires an vegetable oil (unsaturated, contains C=C) and Hydrogen, with a nickel catalyst at 100degrees with 4atm, this leads to production of a saturated hydrocarbon chain, this is margarine.
-------------------------------------------------------------------------
Reactions of Alkenes

Making Dihaloalkanes
Reagents: Alkene + Halogen (NOT F)
Conditions: aqueous solution, room temp

Making Alkanes
Reagents: Alkene + H2
Conditions: Nickel catalyst, 100 degrees, 4 atm

Making Haloalkanes (If this reaction is done with an unsymmetrical isomer, 2 isomeric forms will be produced)
Reagents: Alkene + Hydrogen halide
Conditions: mix in gas phase

Making Alcohols
Reagents: Alkene + H2o (steam)
Conditions: Phosphoric acid catalyst, 100degrees

Addition Polymerisation
Ziegger Natta catalyst at room temp OR 3000atm at 250 degrees (old method)
---------------------------------------------------------------------------

Why is the nature of the carbon chain important when partially oxidising alcohols?

[otrivine]

(Original post by mathsclown)
This is hydrogenation or reduction, it requires an vegetable oil (unsaturated, contains C=C) and Hydrogen, with a nickel catalyst at 100degrees with 4atm, this leads to production of a saturated hydrocarbon chain, this is margarine.
-------------------------------------------------------------------------
Reactions of Alkenes

Making Dihaloalkanes
Reagents: Alkene + Halogen (NOT F)
Conditions: aqueous solution, room temp

Making Alkanes
Reagents: Alkene + H2
Conditions: Nickel catalyst, 100 degrees, 4 atm

Making Haloalkanes (If this reaction is done with an unsymmetrical isomer, 2 isomeric forms will be produced)
Reagents: Alkene + Hydrogen halide
Conditions: mix in gas phase

Making Alcohols
Reagents: Alkene + H2o (steam)
Conditions: Phosphoric acid catalyst, 100degrees

Addition Polymerisation
Ziegger Natta catalyst at room temp OR 3000atm at 250 degrees (old method)
---------------------------------------------------------------------------

Why is the nature of the carbon chain important when partially oxidising alcohols?

because the carbons could be attached to 3 carbons with alchol and this determines if they should either be oxidised to aldehydes ketones carboxylic acid. due to being attached to different carbon atoms

[SpringNicht]

(Original post by mathsclown)
Ehmm havent answered but...I know functional group tests can help to show what type is present but not differentiate members of the same homologous series, need spectroscopy for that? So would spectroscopy be involved in the answer?

They're all different functional groups, 1st is a carboxylic acid, 2nd is an aldehyde and 3rd is a primary alcohol.

Infrared spectroscopy would identify them and quote whatever the wavelength the peaks would be at off the data sheet.

Alternatively you could use a pH indicator to identify the acid, use acidified K2Cr2O7 to oxidise them and distill off the product and pH test that. Aldehyde would be oxidised to a carboxylic acid giving an acidic pH, alcohol would only be oxidised to an aldehyde since we're not refluxing

Oooor, they all have different mass numbers so mass spec would do it!

[mathsclown]

(Original post by SpringNicht)
They're all different functional groups, 1st is a carboxylic acid, 2nd is an aldehyde and 3rd is a primary alcohol.

Infrared spectroscopy would identify them and quote whatever the wavelength the peaks would be at off the data sheet.

Alternatively you could use a pH indicator to identify the acid, use acidified K2Cr2O7 to oxidise them and distill off the product and pH test that. Aldehyde would be oxidised to a carboxylic acid giving an acidic pH, alcohol would only be oxidised to an aldehyde since we're not refluxing

Oooor, they all have different mass numbers so mass spec would do it!

Yup thanks really cleared it up for me. I was thinking along lines of infrared spectoscopy, and using functional group tests to try and show that each one is different, but wasn't too sure Thanks

[Fatima0065]

Hello. im resitting this module and don't understand Hess's cycles. i always get confused with the positive and negative signs. Can anyone help me? thanks...your help is much appreciated

[mathsclown]

(Original post by Fatima0065)
Hello. im resitting this module and don't understand Hess's cycles. i always get confused with the positive and negative signs. Can anyone help me? thanks...your help is much appreciated

Not sure if you've learnt it the same way as I have but i'll try and explain
Just made this now in paint

[Natalie21]

(Original post by mathsclown)
This is hydrogenation or reduction, it requires an vegetable oil (unsaturated, contains C=C) and Hydrogen, with a nickel catalyst at 100degrees with 4atm, this leads to production of a saturated hydrocarbon chain, this is margarine.
-------------------------------------------------------------------------
Reactions of Alkenes

Making Dihaloalkanes
Reagents: Alkene + Halogen (NOT F)
Conditions: aqueous solution, room temp

Making Alkanes
Reagents: Alkene + H2
Conditions: Nickel catalyst, 100 degrees, 4 atm

Making Haloalkanes (If this reaction is done with an unsymmetrical isomer, 2 isomeric forms will be produced)
Reagents: Alkene + Hydrogen halide
Conditions: mix in gas phase

Making Alcohols
Reagents: Alkene + H2o (steam)
Conditions: Phosphoric acid catalyst, 100degrees

Addition Polymerisation
Ziegger Natta catalyst at room temp OR 3000atm at 250 degrees (old method)
---------------------------------------------------------------------------

Why is the nature of the carbon chain important when partially oxidising alcohols?

I was taught that the hydration of alkenes to alcohols requires phosphoric acid catalyst, 300 degrees celsius and 60 atm??

[mathsclown]

(Original post by Natalie21)
I was taught that the hydration of alkenes to alcohols requires phosphoric acid catalyst, 300 degrees celsius and 60 atm??

Just did a google, their were various conditions, including yours and mine, will also have to check markscheme to confirm.

[mathsclown]

Quick question, for F321, if a C is 35, B is 40 and an A is 45 would that mean 55 would be 90/90UMS? Or would it more likely be around 57-58

[Fatima0065]

(Original post by mathsclown)
Not sure if you've learnt it the same way as I have but i'll try and explain
Just made this now in paint

Thankyou!!! this makes more sense..In summary wheny you have enthalpy of formation delta 1=delta2 + delta 3. And enthalpy of cumbustion: delta 1= delta 2-delta 3. However How would I answer questions like this:
Alkane formula Hc/kJ mol-1
Methane CH4 –890
Ethane C2H6 –1560
Propane C3 H8 –2220
(i)
[2]
(iii) Propane can be cracked to form ethene and methane.
C3H8(g)  C2H4(g)  CH4(g)
The standard enthalpy change of combustion of ethene, Hc = –1410 kJ mol-1.
Use this value together with relevant values in Table above to calculate the enthalpy change of this reaction.





H = ......................... kJmol-1
[3]
[Total 7 marks]


16. The carbonates and nitrates of Group 2 elements decompose when heated.
Barium nitrate decomposes when heated to make barium oxide, nitrogen dioxide and oxygen.
2Ba(NO3)2(s) → 2BaO(s) + 4NO2(g) + O2(g)
Calculate the enthalpy change of reaction, ∆Hr, in kJ mol–1, for the thermal decomposition of barium nitrate using the enthalpy changes of formation, ∆Hf, given in the table.
compound ∆Hf /kJ mol–1
Ba(NO3)2(s)
BaO(s)
NO2(g) –992
–558
+33






answer ........................... kJ mol–1
[3]
[Total 3 marks]

[Natalie21]

(Original post by mathsclown)
Just did a google, their were various conditions, including yours and mine, will also have to check markscheme to confirm.

That's good to know Will have to check out a markscheme at some point

[mathsclown]

(Original post by Fatima0065)
Thankyou!!! this makes more sense..In summary wheny you have enthalpy of formation delta 1=delta2 + delta 3. And enthalpy of cumbustion: delta 1= delta 2-delta 3. However How would I answer questions like this:
Alkane formula Hc/kJ mol-1
Methane CH4 –890
Ethane C2H6 –1560
Propane C3 H8 –2220
(i)
[2]
(iii) Propane can be cracked to form ethene and methane.
C3H8(g)  C2H4(g)  CH4(g)
The standard enthalpy change of combustion of ethene, Hc = –1410 kJ mol-1.
Use this value together with relevant values in Table above to calculate the enthalpy change of this reaction.





H = ......................... kJmol-1
[3]
[Total 7 marks]


16. The carbonates and nitrates of Group 2 elements decompose when heated.
Barium nitrate decomposes when heated to make barium oxide, nitrogen dioxide and oxygen.
2Ba(NO3)2(s) → 2BaO(s) + 4NO2(g) + O2(g)
Calculate the enthalpy change of reaction, ∆Hr, in kJ mol–1, for the thermal decomposition of barium nitrate using the enthalpy changes of formation, ∆Hf, given in the table.
compound ∆Hf /kJ mol–1
Ba(NO3)2(s)
BaO(s)
NO2(g) –992
–558
+33






answer ........................... kJ mol–1
[3]
[Total 3 marks]

Oops made 2 mistakes forgot to use MINUS1410 and 2 x enthalpy of Ba(NO3)2...I got 80 and 1000, is that right? I'll send you my solutions if so )

[Fatima0065]

(Original post by mathsclown)
Oops made 2 mistakes forgot to use MINUS1410 and 2 x enthalpy of Ba(NO3)2...I got 80 and 1000, is that right? I'll send you my solutions if so )

Yep thats right! )) can you send me the solutions please. Thankyou

[PrincessMedic]

This time next week...so close! So scared!

[otrivine]

(Original post by PrincessMedic)
This time next week...so close! So scared!

i know so scary we will now be chatting at this time to see what our answers were lool i am not doing that scared to affect other exams ? but do u think this would be a nice paper?

[PrincessMedic]

(Original post by otrivine)
i know so scary we will now be chatting at this time to see what our answers were lool i am not doing that scared to affect other exams ? but do u think this would be a nice paper?

LOL I know! This time, next week we'll be like...'What did you get for...?' and 'I got...' I'll probably be like 'Oh my gosh, I failed!' I really hope it's a nice paper! I'm slowly starting to forget everything!

[otrivine]

(Original post by PrincessMedic)
LOL I know! This time, next week we'll be like...'What did you get for...?' and 'I got...' I'll probably be like 'Oh my gosh, I failed!' I really hope it's a nice paper! I'm slowly starting to forget everything!

when is your first exam ! today i went to college today and i saw they listed all our names to tell us in which room we will be for our exams that was scary

[PrincessMedic]

(Original post by otrivine)
when is your first exam ! today i went to college today and i saw they listed all our names to tell us in which room we will be for our exams that was scary

Yeah, that is scary! I had a 2 and a half hour Young Enterprise exam today morning...it was horrible! Our teacher only 'prepared' us for it a little bit. My first official exam is next week, Monday...Biology unit 1. I have 4 exams next week How about you?

[otrivine]

(Original post by PrincessMedic)
Yeah, that is scary! I had a 2 and a half hour Young Enterprise exam today morning...it was horrible! Our teacher only 'prepared' us for it a little bit. My first official exam is next week, Monday...Biology unit 1. I have 4 exams next week How about you?

got 3 exams next week good luck for bio unit 1! my teacher said that the paper would be easier than jan 2012 cause jan is always harder than june !!? but warning grade boundaries would be high so dont make mistakes