Chemistry Higher Paper

Jumping-Jew

Ok people, whats coming up on this ****e 2moz...?!

madnirvana

Jumping-Jew wrote:

Ok people, whats coming up on this ****e 2moz...?!

be prepared for some twisted chemistry id say:cool:

Jumping-Jew

Thanks, very insightful, ive got my A1 now!!

JC 2K3

How would anyone know what's coming up?

RafaB

Would someone please help me!

heat of neutralisation Exp

Why are polystyrene cups used?

What precautions should be taken to ensure an accurate measure of the rise in temp

If the base used had been ammonia the heat of reaction would have been less. Explain why?

ChainFireMetal

How would anyone know what's coming up

now thats just plain unhelpfull

ZorbaTehZ

There are now 5 different chemistry threads on page 1 ...

rjt

ChainFireMetal wrote:

now thats just plain unhelpfull

I think it's a fair point at this stage. Given that just about every tip and leak has been wrong so far (at least in those I've paid attention to - French, history, physics, Irish, English), I wouldn't put much faith in any predictions.

kisaragi

rjt wrote:

I think it's a fair point at this stage. Given that just about every tip and leak has been wrong so far (at least in those I've paid attention to - French, history, physics, Irish, English), I wouldn't put much faith in any predictions.

Maths was spot on though Difference equation proof and binomial in Q8 saved my ass anyway. I would say Plath was predicted in English but was she ever not going to come up?

For chem you should probably revise organic the most seeing as in it's the largest section and pretty easy...

Polystyrene cups are used because they're insulators right? So they'll retain the heat and lead to a more accurate result yada yada yada

I can't remember the answers to the other ones shows how well I'm going to do

Jumping-Jew

Ok let me rephrase this due to some of ye people!

Please write your views on what you believe will come up in the paper 2moz...

madnirvana

RafaB wrote:

Would someone please help me!

heat of neutralisation Exp

Why are polystyrene cups used?
Becauese they are good insulators.

What precautions should be taken to ensure an accurate measure of the rise in temp.
stir throughout experiment, dont splash, use sensitive thermometer

If the base used had been ammonia the heat of reaction would have been less. Explain why?

??

naus

Lid and ensure both acid and base are same temp before mixing

Ammonia is not as strong a base as NaOH

RafaB

Thanks!!

jaydigity

Jumping-Jew wrote:

Ok let me rephrase this due to some of ye people!

Please write your views on what you believe will come up in the paper 2moz...

Rightio,
-Ethanoic acid
-Heat of neutralisation
-Redox titrations (perhaps bleach)
-A q on clove oil exp
-Chemical equilibrium mathematical workings out

However I've still got a bitter taste in my mouth after history so
DO NOT LEAVE ANYTHING OUT!!!!
Ethene has come up on the chem paper three years in a row, they are absolute sadists.Personnally, I don't think ethanoic acid will come up,simply because its so hotly tipped

Lucas10101

Heat of Neutralisation and Ethanoic Acid and Bleach haven't been up and are really expected, would be very very surprised if one of these three didn't appear in section A, maybe a section B appearance.

Why are polystyrene cups used?

Polystyrene Cups are used because there considered to be of negligible heat capacity and won't affect the calculations. The main reason is to retain heat. Plus the lids ensure that heat is kept in.

What precautions should be taken to ensure an accurate measure of the rise in temp

The solutions should both be at the same temperature before adding the base to the acid. Care should be taken to ensure no loss of liquid when the two solutions are mixed. Stir the solution with a stirring rod to get the maximum rise in temperature. Mix the solutions very quickly. Make sure you note the highest temperature reach. Use a cover to prevent heat loss.

If the base used had been ammonia the heat of reaction would have been less. Explain why?

Ammonia can act as an acid as far as I know in some reactions and is a weaker base although I'm not really sure about these two reasons, I however would write them down in an exam.

nedward

Ammonia needs more energy as it is weak, and more energy is required to break the bonds and dissociate, whereas NaOH will dissociate freely. Heat of neutralisations for weak acids/bases are generally lower than 57-55 kJ because of this.

Lucas10101

Actually, go to page 329 of Chemistry Live, the reason for the Weak Base in Ammonia is given at the top.:)

When either a Weak Acid or a Weak Base is involved, the value for delta H is less than 57kJmol-1, the reason for this is because a weak acid or weak base is not fully dissociated in water. The weak acid/base must be fully dissociated but this requires energy, thus an Endothermic reaction takes place because heat is required to cause complete dissociation and the value will be less than 57...probably -52.2kJmol-1

cson

****ing chemistry.

Assez Bien

Hey u ^^^ how u fixed 4 2morro? Wat time u comin in at 2morro....i may need a hand crammin stuff into my fragile little mind!!

cson

You've had like 7 days off to study for this! Unlike poor moi who had to endure accounting today.

Assez Bien

Well my liver has endured many beerin sessions in those 7 days sir!! I only started studyin 2day and that was jus flicking thro the revision book while watchin tv n straightenin my hair 4 lik the millionth time!!

cson

I think we're after hijacking this thread....check your PMs and we shall continue this conversation.

So yeah, ethanoic, rates rxn etc etc