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OCR chemistry chains and rings jan 10th 2007

trickz

The one where incomplete combustion will produce Carbon monoxide which is toxic?

wow ..didnt get that hehe .The equation before was it just regular combustion, as i didnt include carbon monoxide :frown:

Reply 41

trickz

OP

10

Could be that actually dani2511 :smile:

Reply 42

dani2511

2

trickz

The one where incomplete combustion will produce Carbon monoxide which is toxic?

lol... that's probably the answer they were looking for... i had a blonde moment :biggrin:

Reply 43

trickz

OP

10

tIT4tOe

wow ..didnt get that hehe .The equation before was it just regular combustion, as i didnt include carbon monoxide :frown:

yeh but incomplete combustion could occur :wink:

Reply 44

dani2511

2

what did you put for the conclusion part? (this has already been asked, but i was the only one that answered...)

Reply 45

Miss_Scarlett

15

trickz

The one where incomplete combustion will produce Carbon monoxide which is toxic?

I put that. Im not sure its right tho, coz propane is a small hydrocarbon therefore making it more likely for it too fully combust.

EDIT: I know the grade boundary for an A is usually 48, and I dont want to start conspiring about what it will or wil not be this yr :biggrin:

(

) but any ideas, think it wil stay the same (most likely) or go down a bit?

Reply 46

Andy Conda

2

trickz

yeh but incomplete combustion could occur :wink:

im know good at thinking outside the box *sigh* :mad:

Reply 47

Andy Conda

2

Miss_Scarlett

I put that. Im not sure its right tho, coz propane is a small hydrocarbon therefore making it more likely for it too fully combust.

Carbon Monoxide is better answer than mine. I put it produces CO2 will in a non-ventillated area can cause breathing issues !! lmao like what the *zzz* . o well

Reply 48

Miss_Scarlett

15

dani2511

what did you put for the conclusion part? (this has already been asked, but i was the only one that answered...)

Is this the one with Br? For the first bit I said it contained a C=C, as obv it decolurises the sol.

For the second one, wasnt sure so just put that it showed that an Electrophillic addition reaction had taken place.

Reply 49

uksangho2000

im a retake as well and surprisingly i thought this paper was much much easier that Jun 2007 which is messed up from the answers i remember,

igot c10h18o for something
and for the question why shouldn't you use propane in unventilated area i put that it could lead to incomplete combustion and producing carbon monoxide, the word UNVENTILATED gives it away so i think that is right.

and for the last essa question it was easy marks:
when halogenoalkanes react with water, it gives off a alcohol and a hailide
and the rate of reaction could be measured by the time of precipitation when silver nitrate is added, and you have to talk about the Electronegativity and Bond enthalpy between all 3 halogenoalkane, and ofcourse Bond enthalpy has greater effect, therefore Iodide will have the fastest reaction and i just wrote the equations of the reactions, which hopefully i will get right

Reply 50

t3h_on3

I resat this as well..and it wasn't too bad imo. The final question was a bit tricky, but overall it went pretty good..I think the only thing that was a bit iffy for me was "why is propane unreactive?" or something along those lines..I just said it was non-polar but didn't go into depth.

For the bromine bit i think i got 0.04 moles..but i forgot to times bromine by 2 as it's diatomic so I know I got that wrong..and the bit after where it said "what does this investigation show us..I put, it has 2 c=c bonds..but that was just a guess. Hopefully I'll get an A this time round.

Reply 51

Maximus

To get full marks for the last question:

Rates of reactivity: R-I > R-Br > R-Cl
Reactivity of halogenoalkanes depends on breaking carbon-hal bond, carbon-iodide bond weakest and carbon-chlorine bond is strongest. (2 marks)

Equation: Ag+ (aq)+ X- (aq) > AgX (s) (1mark)

Add equal volumes of (aq) ethanolic silver nitrate and three comparable halogenoalkanes to three separate test tubes and warm the mixture to 40C and time the first appearance of a silver halide precipitate. (3 marks)

1 mark for qwc awarded :wink:

Reply 52

Andy Conda

2

Maximus

To get full marks for the last question:

Rates of reactivity: R-I > R-Br > R-Cl
Reactivity of halogenoalkanes depends on breaking carbon-hal bond, carbon-iodide bond weakest and carbon-chlorine bond is strongest. (2 marks)

Equation: Ag+ (aq)+ X- (aq) > AgX (s) (1mark)

Add equal volumes of (aq) ethanolic silver nitrate and three comparable halogenoalkanes to three separate test tubes and warm the mixture to 40C and time the first appearance of a silver halide precipitate. (3 marks)

1 mark for qwc awarded :wink:

It was worth 9marks so ummm

Reply 53

Maximus

tIT4tOe

It was worth 9marks so ummm

Yeah I know it was worth nine marks, there will be variables in the answer that could be worth more or less marks. However, a structured answer like that would get you close to the full nine marks.

Reply 54

Andy Conda

2

Maximus

Yeah I know it was worth nine marks, there will be variables in the answer that could be worth more or less marks. However, a structured answer like that would get you close to the full nine marks.

im guessing you would achieve marks for stating reagents, describing the role of OH ect, colours of ppt. ..

Reply 55

Don't Ask Me

trickz

The one where incomplete combustion will produce Carbon monoxide which is toxic?

I think I put that it creates CO2 and breathing too much CO2 is harmful, d'you reckon it'd get the mark?

Reply 56

Andy Conda

2

Don't Ask Me

I think I put that it creates CO2 and breathing too much CO2 is harmful, d'you reckon it'd get the mark?

That's what i put, seemed to obvious though, so i doubt it'll achieve the mark.. :frown:

Reply 57

dani2511

2

tIT4tOe

That's what i put, seemed to obvious though, so i doubt it'll achieve the mark.. :frown:

sometimes it's the most obvious things that they are looking for. i said because it's highly flammable... how blonde!

Reply 58

Maximus

tIT4tOe

im guessing you would achieve marks for stating reagents, describing the role of OH ect, colours of ppt. ..

Yes probably, my initial answer is just a rough guide.

The question that asked to state the molecular formula quite a few people were annoyed with, they were programmed to think 'you have to divide the molecular mass by the mass of the empirical formula'. Yeah, your C10H18O is correct.

Reply 59

bella127

11

For the propane one marker.. it said about why it should always be used in a well-ventilated area. I took my clue from that, and wrote:

Without an excess of oxygen, there is a risk that propane could incompletely combust to give carbon monoxide, a poisonous gas.

OCR chemistry chains and rings jan 10th 2007

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