OCR Chemistry F322~ 4th June 2013~ AS Chemistry

Original post by TheFootyKing19

Great answers! Say orange to colorless for decolourises :wink:

haha i was 50/50 about orange or brown. thanks!

Reply 1921

Jimmy20002012

OP

4

Original post by Ché.

In terms of the full UMS cap conversion in F322, what will that exactly be?
I know the grade boundaries are quite high, but just out of interest!?
:biggrin:

94/100

Reply 1922

Ché.

Original post by needtosucceed=)

defintions right.
thats correct, an easier way of saying it would be that bond enthalpy values arent the same as average bond enthalpy vaues :smile:

Thaaaaaaaaaanks!

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Reply 1923

Hardworker?

1

can someone give the conditions for all the reactions that we need to know about? (equations are not necessary)

Reply 1924

Ché.

Original post by Jimmy20002012

94/100

Really!?
Okay,

I just about got that in this mock examination then; I would have though full marks WAS full marks
LOL.

THANK YOU VERY MUCH, ANYWAY. :biggrin:

Reply 1925

JimmyA*

Has there actually been any questions on the ziegler-natta catalyst or the haber process?

Reply 1926

ellalouiseanne

can someone help me on question 3bii ? http://www.ocr.org.uk/Images/78566-question-paper-unit-f322-chains-energy-and-resources.pdf i don't get how they get -792 kJmol-1 for the enthalpy change of formation?

Reply 1927

Blashnet

8

Two workers decide to car-share on a 25 mile journey to work and back. On this journey, each of their cars uses petrol equivalent to 2.0 kg of heptane.

Assuming such car-sharing, use your equation(complete combustion of heptane) to:
(i) calculate the amount, in mol, of heptane, C7H16, saved;
(ii) calculate the energy saved (Hc o [C7H16] = – 4817 kJ mol–1);
(iii) calculate the decrease in volume of CO2(g) emitted into the atmosphere. Assume that the conditions are the same as room temperature and pressure.
[2]
[1]
[2]

help!

Reply 1928

Original post by GeneralOJB

further maths in a year(as+a2) and physics a2. I'm doing extra maths modules too for 'additional further maths' lul

you'll be fine with a2 then lol

Reply 1929

Joey952

12

Original post by needtosucceed=)

work out the moles for each one then divide one by the other and x100

ignore the tonnes just work in grams.

still can't do it :frown:

Reply 1930

Kits

I got a medium B in Jan
Got like 39 on coursework

What do I need to do in this exam for an A? Will scraping an A be enough or do I have to smash it

Reply 1931

Beths_7

7

What's everyone doing tonight for last minute revision?! I've done all past papers etc but really feel like I should be doing something tonight to prepare.
I'm very nervous!

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Reply 1932

JimmyA*

Original post by GeneralOJB

further maths in a year(as+a2) and physics a2. I'm doing extra maths modules too for 'additional further maths' lul

Well if you want to do maths then obviously you need maths and further maths. Physics and Chemistry are both hard so choose your favourite or the one which you get the highest in so you can concentrate on your maths mostly.

Reply 1933

Original post by Blashnet

Two workers decide to car-share on a 25 mile journey to work and back. On this journey, each of their cars uses petrol equivalent to 2.0 kg of heptane.

Assuming such car-sharing, use your equation(complete combustion of heptane) to:
(i) calculate the amount, in mol, of heptane, C7H16, saved;
(ii) calculate the energy saved (Hc o [C7H16] = – 4817 kJ mol–1);
(iii) calculate the decrease in volume of CO2(g) emitted into the atmosphere. Assume that the conditions are the same as room temperature and pressure.
[2]
[1]
[2]

help!

- moles/molar mass.
- q=deltaH x n (when calculating n multiply your previous answer by 7 as theres 7 moles of co2 in the equation u wrote for the other question)
- volume = n x 24

use those equations, if you're still stuck lemme know.

Reply 1934

Josh989

Hi just wondering if someone could help me, by looking through my textbox it says; enthalpy change of formation is 'sum of enthalpy of PRODUCTS - sum of enthalpy of REACTANTS'
However I have come across this question;
The standard enthalpy change of formation of hexane can be determined indirectly.
Calculate the standard enthalpy change of formation of hexane using the standard
enthalpy changes of combustion below.
substance Hc / kJ mol–1
C –394
H2 –286
C6 H14 –4163
Equation; 6C + 7H2 -------> C6H14
And the answer is -203...
However I got +203 when I did it with the original equation??? Is it because all the reactants/product are minus so the answer follows? Or because the forward reaction is exothermic so the H change follows?? Little confused :frown:

If you could help in anyway I would be very greatful!!! Exam tomorrow :O!!!

Reply 1935

Original post by Kits

I got a medium B in Jan
Got like 39 on coursework

What do I need to do in this exam for an A? Will scraping an A be enough or do I have to smash it

what was your ums for unit 1?

Reply 1936

JimmyA*

Original post by Beths_7

What's everyone doing tonight for last minute revision?! I've done all past papers etc but really feel like I should be doing something tonight to prepare.
I'm very nervous!

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Going through all the definitions and going over all the green chemistry as there wasn't much in January and i'm rubbish at green chemistry.

Reply 1937

Jonma

Do you have to learn all of the fractions and their uses in fractional distillation, or just the process? I noticed that a fact recall for it has never come up.

Reply 1938