OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

that exam was ok. It wasn't as good as it could have been, but it was okay. I accidentally put percentage yield instead of atom economy, and I couldn't do the shapes question, and I accidentally put propyl ethanoate instead of ethyl propanoate but otherwise...

Reply 941

racheatworld

17

Original post by lolo-x

Is the general formula for an alcohol CnH2n+2O? And was the molecular formula for a 13 carbon alcohol C13H28O?

General formula of alcohol - CnH2n+1OH

Your molecular formula of the 13 Carbon alcohol is what I got :smile:

Reply 942

viksta1000

15

Original post by Cookies and Cream

but it gave the unit as KJmol-1 which surely means per mole already...? I just left it as 66 :smile:

No, they we're the values in the table

You needed to use the delta H value given near the equation which was +66

The equation's stolchiometry showed that two moles of NO were formed

Reply 943

montanaj

Original post by chargedmachine

I put that an internal combustion engine isnt really a closed system, I.E. it has an exhaust...so dynamic equilibrium can't be reached. Is that right?

That's what I put, pretty sure it's right :smile:

Reply 944

racheatworld

17

Original post by NRT

For the second one, yeah i put C13H27OH but its all the same.

I'm not sure it is, I don't think C13H27OH is a molecular formula.

Reply 945

lolo-x

Original post by racheatworld

General formula of alcohol - CnH2n+1OH

Your molecular formula of the 13 Carbon alcohol is what I got :smile:

Hmm do you think I'd get the mark for CnH2n+2O? It's the same thing really..

Reply 946

NRT

Original post by racheatworld

I'm not sure it is, I don't think C13H27OH is a molecular formula.

CGP Chem AS guide use butanol as an example for their definition of a molecular formula and put it in the form C4H9OH, so it seems fine, but they are both the same i think.

Reply 947

Flint_09

8

Original post by |Alex

No. If you drink methanol you will kill yourself.

the fact is Methanol can be used to make alcoholic drinks, then whether u drink it or not is upto u

Reply 948

montanaj

Original post by Flint_09

the fact is Methanol can be used to make alcoholic drinks, then whether u drink it or not is upto u

Lol, I'm not sure if the mark scheme will see it that way :P

Reply 949

lolo-x

Original post by Flint_09

the fact is Methanol can be used to make alcoholic drinks, then whether u drink it or not is upto u

fairplay... although you wouldn't class petrol or vinegar or something else disgusting as a drink, although in theory you can drink them, so idk if that argument works.. haha

Reply 950

kimmey

7

Original post by NRT

Messed up the last question, but overall was not too bad. Was surprised at the lack of maths required but hey.
From what i can remember this is what i got : just a little note i doubt that these will be correct.
Enthalpy change of combustion is the enthalpy change when 1 mole of a substance is completely burnt in oxygen (No need to mention standard conditions here as it didn't ask for standard enthalpy change.
Got -1279 for the enthalpy change.
+33 for the enthalpy change of formation.
Messed up the Ozone one.
Atom economy is important as in industry we require more sustainable systems where little waste is produced, both for the environment and so that the most is made from expensive reactants.
International cooperation is important to raise awareness for governments and people to recycle/ dispose of plastics carefully.
Burning of chloroethene creates TOXIC HCL gas and TOXIC CO which attaches to haemoglobin better than O2. CO2 contributes to greenhouse effects etc.
The first 4 alcohols are liquids as their molecules hydrogen bond with each other hence these are much stronger than the van der waals that act upon alkanes. The hydrogen bonding occurs from the difference in electronegativity between O and H in the OH group.
A Functional group is a group attached to and organic compound and determines its chemical properties.
The reason why poly methanol dissolves in water is because it hydrogen bonds with it.
The 10 marker in the middle was heterolytic fission, nucleophilic substitution, C-Cl bonds are the strongest and shortest. Drawing the diagram with curly arrows etc is probably 4 marks and you had to do an equation too.
The last one was ethyl propanoate which was the modal answer in my college
The shape one i put tetrahedral and linear, the latter appearing incorrect.
Incomplete combustion CH3OH + O2 -> CO + 2H2O
Complete combustion CH3OH + 1.5O2 -> CO2 + 2H2O
Hope this helps with making an initial markscheme, ill add more when my memory is a little less vague :smile:

[/

i have a question..... basically for the incomplete combustion and complete combustion which way round did they ask the question ? did they ask for the complete combustion equation first and then the incomplete or was it the other way round cus im afraid tht i filled it in the wrong way ????? thanks :smile:

Reply 951

lolo-x

Original post by NRT

CGP Chem AS guide use butanol as an example for their definition of a molecular formula and put it in the form C4H9OH, so it seems fine, but they are both the same i think.

i put CnH2n+1OH originally and then decided to change it to CnH2n+2O, do you think they will let me have the mark? :/

Reply 952

amyyy24

11

Original post by NRT

i have a question..... basically for the incomplete combustion and complete combustion which way round did they ask the question ? did they ask for the complete combustion equation first and then the incomplete or was it the other way round cus im afraid tht i filled it in the wrong way ????? thanks :smile:

It was complete then incomplete, changed it on that semi-mark scheme thing :smile:

Reply 953

medusa cascade

If you drink methanol, you'll go blind.

Incidentally, a treatment for methanol poisoning is to drink lots of alcohol, because the molecules are approximately the same shape =P

Reply 954

NRT

Original post by lolo-x

i put CnH2n+1OH originally and then decided to change it to CnH2n+2O, do you think they will let me have the mark? :/

Yeah it should be fine 99% sure. I've done it and its been ok before.

Reply 955

lolo-x

Original post by NRT

Yeah it should be fine 99% sure. I've done it and its been ok before.

oh nice one, thanks :smile:

Reply 956

Flint_09

8

Original post by montanaj

Lol, I'm not sure if the mark scheme will see it that way :P

we shall see what the ms says
but i'm not sure though... it asked "large scale use of methanol", therefore i may be wrong coz obviously no one drinks methanol as it is a KILLER

Reply 957

racheatworld

17

[QUOTE="kimmey;31756535"]

Original post by NRT

Messed up the last question, but overall was not too bad. Was surprised at the lack of maths required but hey.
From what i can remember this is what i got : just a little note i doubt that these will be correct.
Enthalpy change of combustion is the enthalpy change when 1 mole of a substance is completely burnt in oxygen (No need to mention standard conditions here as it didn't ask for standard enthalpy change.
Got -1279 for the enthalpy change.
+33 for the enthalpy change of formation.
Messed up the Ozone one.
Atom economy is important as in industry we require more sustainable systems where little waste is produced, both for the environment and so that the most is made from expensive reactants.
International cooperation is important to raise awareness for governments and people to recycle/ dispose of plastics carefully.
Burning of chloroethene creates TOXIC HCL gas and TOXIC CO which attaches to haemoglobin better than O2. CO2 contributes to greenhouse effects etc.
The first 4 alcohols are liquids as their molecules hydrogen bond with each other hence these are much stronger than the van der waals that act upon alkanes. The hydrogen bonding occurs from the difference in electronegativity between O and H in the OH group.
A Functional group is a group attached to and organic compound and determines its chemical properties.
The reason why poly methanol dissolves in water is because it hydrogen bonds with it.
The 10 marker in the middle was heterolytic fission, nucleophilic substitution, C-Cl bonds are the strongest and shortest. Drawing the diagram with curly arrows etc is probably 4 marks and you had to do an equation too.
The last one was ethyl propanoate which was the modal answer in my college
The shape one i put tetrahedral and linear, the latter appearing incorrect.
Incomplete combustion CH3OH + O2 -> CO + 2H2O
Complete combustion CH3OH + 1.5O2 -> CO2 + 2H2O
Hope this helps with making an initial markscheme, ill add more when my memory is a little less vague :smile:

[/

i have a question..... basically for the incomplete combustion and complete combustion which way round did they ask the question ? did they ask for the complete combustion equation first and then the incomplete or was it the other way round cus im afraid tht i filled it in the wrong way ????? thanks :smile:

They asked complete then incomplete.

Reply 958

NRT

Original post by kimmey

i have a question..... basically for the incomplete combustion and complete combustion which way round did they ask the question ? did they ask for the complete combustion equation first and then the incomplete or was it the other way round cus im afraid tht i filled it in the wrong way ????? thanks :smile:

Sorry im not too sure i think it was complete first. But im seriously 50/50 it was only 2 marks so don't worry too much about it.

Reply 959

broken_glass_heart

Iv totally failed that exam! I was so short of time, didn't have time to answer all da questions and i ended up missing out the hole of both 10mark questions - theres my 20marks thrown away so easily! :frown:

OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

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