***2013 LC Chemistry Before/After***

KildareKing

TheChosenOne wrote: »

No, the diagram was right in this regard. Water should always flow in from the bottom so it moves slowly around the tube

damn it I hope the 2 extra questions will cover me then.

KildareKing

KildareKing wrote: »

noooo are you serious...

Although I looked up the curriculum there and we are not required to know the reaction of ethanol with Mg so maybe they might give it to us?

yoppo

Deleted User wrote: »

Although I looked up the curriculum there and we are not required to know the reaction of ethanol with Mg so maybe they might give it to us?

Are you sure? We done it in class. It forms sodium ethoxide :cool:

SecondMan

yoppo wrote: »

Are you sure? We done it in class. It forms sodium ethoxide :cool:

Same as us

xJEx

What were the ansers for question 3?
ike the burette - i said it would measure a more accurate volume but that it would be slow to add it so would affect accuracy in measuring the temp rise.
and then i said to measure it as accurately as possibe add quickly plus a lid to avoid heat loss?

oh and for the last bit i said a the lower concentrations would have given a slower reaction so more time for heat losses

MarieCurie22

Deleted User wrote: »

Sounds familiar anyway!

F*ck so hang on I took it as the molarity and didnt divide anything at the end? Ii got 4.3kj/mol?

a sure look i did all 3 experiments and an extra question my a** is safe in the A2 and probably A1

Glee_GG

xJEx wrote: »

What were the ansers for question 3?
ike the burette - i said it would measure a more accurate volume but that it would be slow to add it so would affect accuracy in measuring the temp rise.
and then i said to measure it as accurately as possibe add quickly plus a lid to avoid heat loss?

oh and for the last bit i said a the lower concentrations would have given a slower reaction so more time for heat losses

I remember at some stage our teacher told us that you don't put a base in the burette because it tends to jam the tap and the opening over time so I just wrote that down, couldn't really think of anything else!

yoppo

xJEx wrote: »

What were the ansers for question 3?
ike the burette - i said it would measure a more accurate volume but that it would be slow to add it so would affect accuracy in measuring the temp rise.
and then i said to measure it as accurately as possibe add quickly plus a lid to avoid heat loss?

oh and for the last bit i said a the lower concentrations would have given a slower reaction so more time for heat losses

A) Definition
Polystyrene
C) More accurate, bases cause the tap to stick
D) Use digital thermometer and use a lid to minimize heat loss
E) Basic calculation
F) Corrosive, burn your skin. Triangle symbol with the test tube and hand.

MarieCurie22

yoppo wrote: »

A) Definition
Polystyrene
C) More accurate, bases cause the tap to stick
D) Use digital thermometer and use a lid to minimize heat loss
E) Basic calculation
F) Corrosive, burn your skin. Triangle symbol with the test tube and hand.

For disadvantage would they accept takes longer to accurately measure?

And what about stirring and using a standard mercury thermometer with more graduations on it and of a low specific heat capacity?

yoppo

yoppo wrote: »

Are you sure? We done it in class. It forms sodium ethoxide :cool:

We didnt do it :0

yoppo

MarieCurie22 wrote: »

For disadvantage would they accept takes longer to accurately measure?

And what about stirring and using a standard mercury thermometer with more graduations on it and of a low specific heat capacity?

Longer yeah but its still accurate!

Stirring is alright, more graduations I dunno. Human error still could mess that up. In fairness the marking scheme could say anything!

MarieCurie22

yoppo wrote: »

Longer yeah but its still accurate!

Stirring is alright, more graduations I dunno. Human error still could mess that up. In fairness the marking scheme could say anything!

yeah is it just me or was this a "harder" paper....you know some years there like and then last year it was:):P ?

xJEx

Is adding quickly alright for a way of ensuring accuracy?

And can you not say the burette would take longer to add so thats a disadvantage? like the burette takes soooo long to empty so the heat rise would be totally inaccurate cause you'd loose loads of heat to surrounding by the time you had added it all?

MarieCurie22

Is it ok for q 5 when dealing with bohrs theory being modified to talk about the exsistance of sublevels??

Glee_GG

Actually for Q6 the bit on benzene what did ye write for the two parts? We had a paragraph on benzene in general but I wasn't too sure about how to go about splitting it up?

yoppo

MarieCurie22 wrote: »

yeah is it just me or was this a "harder" paper....you know some years there like and then last year it was:):P ?

I want the A1 so I had some nerves going in. Bits of it were sticky but overall is was no more difficult. I messed up the calculations slightly in one bit but its not like maths where it carries on. It's one mark for each maths slip! The main theory was easy enough. I'll find out in August!

MarieCurie22

yoppo wrote: »

I want the A1 so I had some nerves going in. Bits of it were sticky but overall is was no more difficult. I messed up the calculations slightly in one bit but its not like maths where it carries on. It's one mark for each maths slip! The main theory was easy enough. I'll find out in August!

Im pretty sure I nabbed my A1....did extra qs to be sure...girls left early in mine in tears so youre lucky

yoppo

Glee_GG wrote: »

Actually for Q6 the bit on benzene what did ye write for the two parts? We had a paragraph on benzene in general but I wasn't too sure about how to go about splitting it up?

I wrote carbon has 3sp2 hybridized orbitals which is uses to form two sigma bonds to two other carbons and one hydrogen.

for part (ii) i wrote carbon then uses its p orbitals which are above and below the plane of the ring to form pi bonds with carbon using its 6 pi electrons. These 6 pi electrons are delocalised in the ring inferring extra stability which means it has resonance structures. Then I drew benzene.

MarieCurie22

Yo yoppo did you do the moles per litre of I2 AND O2 did you see that? Also is the steam trap the flaw? cause tbh the taps are fine to me?

yoppo

MarieCurie22 wrote: »

Yo yoppo did you do the moles per litre of I2 AND O2 did you see that? Also is the steam trap the flaw? cause tbh the taps are fine to me?

it was: 200 x Mol I2/1 = 9.4 x .02/2

Because it's 2:1 (said in ques), divide answer above by 2 to get moles/L

Then x32 to get g/L
Then x1000 to get mg/L
Thats your answer in ppm

MarieCurie22

yoppo wrote: »

it was: 200 x Mol I2/1 = 9.4 x .02/2

Because it's 2:1 (said in ques), divide answer above by 2 to get moles/L

Then x32 to get g/L
Then x1000 to get mg/L
Thats your answer in ppm

Ii just did V1M1 N1 using different N1s for Oxygen again i was just wondering...and wbu the flaw in q2?

TheChosenOne

yoppo wrote: »

it was: 200 x Mol I2/1 = 9.4 x .02/2

Because it's 2:1 (said in ques), divide answer above by 2 to get moles/L

Then x32 to get g/L
Then x1000 to get mg/L
Thats your answer in ppm

Wait wait, so I2 is simple calculation, no dividing by two, and you divide by two only in part (i) which asks for Oxygen, right?

woopah92

MarieCurie22 wrote: »

Is it ok for q 5 when dealing with bohrs theory being modified to talk about the exsistance of sublevels??

I think they were looking for the electrons move in a wave motion not in a fixed orbit like Bohr thought.
Not sure sublevels would be right, could be though you never know with the marking scheme.

MarieCurie22

woopah92 wrote: »

I think they were looking for the electrons move in a wave motion not in a fixed orbit like Bohr thought.
Not sure sublevels would be right, could be though you never know with the marking scheme.

it said one other....which suggests there was more than one answer....

Glee_GG

MarieCurie22 wrote: »

Is it ok for q 5 when dealing with bohrs theory being modified to talk about the exsistance of sublevels??

The fact that it didn't account for orbitals and sub-levels is a valid point.

woopah92

yoppo wrote: »

A) Definition
Polystyrene
C) More accurate, bases cause the tap to stick
D) Use digital thermometer and use a lid to minimize heat loss
E) Basic calculation
F) Corrosive, burn your skin. Triangle symbol with the test tube and hand.

The last time it was asked, digital thermometer wasn't accepted as full marks #justsaying

TheChosenOne

Where are those college people who just write out the solutions to every question? XD

xJEx

woopah92 wrote: »

I think they were looking for the electrons move in a wave motion not in a fixed orbit like Bohr thought.
Not sure sublevels would be right, could be though you never know with the marking scheme.

Yeah you can say it didnt explain the discovery of subelevels! There'es loads of reasons.. I just said only worked well for hydrogen and not for atoms with more than 1 electron

weirdspider

KildareKing wrote: »

same and I put an arrow pointing towards it and wrote "this is hand"

Loool describing those symbols is so funny. I was like "hand with test tube dropping liquid"

yoppo

TheChosenOne wrote: »

Wait wait, so I2 is simple calculation, no dividing by two, and you divide by two only in part (i) which asks for Oxygen, right?

I did divide by two. I said that above! Sure it's a 2:1 ratio!

yoppo

MarieCurie22 wrote: »

Ii just did V1M1 N1 using different N1s for Oxygen again i was just wondering...and wbu the flaw in q2?

I said the steam valve should be in the water and also they should have included a steam trap.

yoppo

TheChosenOne wrote: »

Where are those college people who just write out the solutions to every question? XD

That would be me! Yoppo BSc (Chemistry) Hons circa 2008.

MarieCurie22

yoppo wrote: »

That would be me! Yoppo BSc (Chemistry) Hons circa 2008.

wait what you have a degree and sat the paper today?

yoppo

MarieCurie22 wrote: »

wait what you have a degree and sat the paper today?

Yip. Doing my Leaving again! Last time I done it was 2003 :pac:

MarieCurie22

yoppo wrote: »

Yip. Doing my Leaving again! Last time I done it was 2003 :pac:

you crazycrazy person!!!!!!!! why!!!?

MarieCurie22

what other subjects are you doing?

yoppo

MarieCurie22 wrote: »

you crazycrazy person!!!!!!!! why!!!?

Because I only got a 2:2 in my degree and want to do med. Can't do grad med with it. I needed a 2:1 but missed out by 2%....

Biology, Physics, Farming, Home Ec, Hons Maths, Pass English.

Physics, farming and Hons Maths are new.

Hamza Malik

Did 9 questions questions 1, 4, 5 and 6 were great

The mechanism question was good too

Q 2 and 9 and 8 were iffy

And I also did question 3 in the end which was ok. Hopefully I got a B1 or even an A2. One can dream.

yoppo

For question 8 it said reagent not condition so hopefully they will take HCL and UV Light!

Hazardous Garden Of Eden

These are my answers to the calculation questions, hopefully they ring a bell :P

Q1(f)
Concentration of I2 = 4.7x10^-4 mol/L
(i) Concentration of O2 = 2.35x10^-4 mol/L
(ii) 7.52x10^-3 g/L
(iii) 7.52 ppm

Q3(e)
Heat produced = 4.342 kJ
Heat of reaction = -57.89 kJ/mol

Q4(c)
How many neutrons = 4.8x10^22

Q6(c)
Heat change = -126.4 kJ/mol

Q9(c)
Kc = 123

Q10(b)(ii)
Mass of aluminium = 346.75 g
Mass of Aluminium Oxide = 1032.75 g

Q10(c)(iv)
Fraction of mass = 1/8

Q11(b)
pH = 11.278

MarieCurie22

Hazardous Garden Of Eden wrote: »

These are my answers to the calculation questions, hopefully they ring a bell :P

Q1(f)
Concentration of I2 = 4.7x10^-4 mol/L
(i) Concentration of O2 = 2.35x10^-4 mol/L
(ii) 7.52x10^-3 g/L
(iii) 7.52 ppm

Q3(e)
Heat produced = 4.342 kJ
Heat of reaction = -57.89 kJ/mol

Q4(c)
How many neutrons = 4.8x10^22

Q6(c)
Heat change = -126.4 kJ/mol

Q9(c)
Kc = 123

Q10(b)(ii)
Mass of aluminium = 346.75 g
Mass of Aluminium Oxide = 1032.75 g

Q10(c)(iv)
Fraction of mass = 1/8

Q11(b)
pH = 11.278

Are you sure about all these?

mocker2012

Hazardous Garden Of Eden wrote: »

These are my answers to the calculation questions, hopefully they ring a bell :P

Q1(f)
Concentration of I2 = 4.7x10^-4 mol/L
(i) Concentration of O2 = 2.35x10^-4 mol/L
(ii) 7.52x10^-3 g/L
(iii) 7.52 ppm

Q3(e)
Heat produced = 4.342 kJ
Heat of reaction = -57.89 kJ/mol

Q4(c)
How many neutrons = 4.8x10^22

Q6(c)
Heat change = -126.4 kJ/mol

Q9(c)
Kc = 123

Q10(b)(ii)
Mass of aluminium = 346.75 g
Mass of Aluminium Oxide = 1032.75 g

Q10(c)(iv)
Fraction of mass = 1/8

Q11(b)
pH = 11.278

I got the same answers as far as i can remember!!

xJEx

I don't think the aluminium one is right there - more like 432g and 816g

yoppo

MarieCurie22 wrote: »

Are you sure about all these?

Q6, 10c and 11 are right. I changed the temperature for the specific heat capacity to kelvin so I made a slip there (thank you physics!)....

MarieCurie22

xJEx wrote: »

I don't think the aluminium one is right there - more like 432g and 816g

Thats what i got too

Hazardous Garden Of Eden

MarieCurie22 wrote: »

Are you sure about all these?

The 10(b) ones I'm not sure cos I did them in a hurry towards the end of the exam, but the others I think (I hope) I'm right!

wow exuberant

yoppo wrote: »

Q6, 10c and 11 are right. I changed the temperature for the specific heat capacity to kelvin so I made a slip there (thank you physics!)....

I don't think the kc value is right

xJEx

Yoppo how did you find physics ? )

SecondMan

xJEx wrote: »

I don't think the aluminium one is right there - more like 432g and 816g

Same

Nl90

I'm so mad at myself !
I did all my calculations wrong!
PH , Kc , and winkler method!
Couldn't focus at all
Had some mistakes in ex2
Do you think I might get a B2 ?!