Sweet sweet chemistry

deek

Just imagine if benzoic acid came up :eek: god im gonna wash my mouth out with soap for even mentioning it.Its something to do with recrystllisation right

deek

Oh if only my sig applied to the leaving cert..........

Cherry_Pie

Look over recrystalisation now!!! Its a very very very easy experiemnt with basically nothing in the way of equations to learn!!!! take u 10 mins!!

deek

No Ive had a week off between exams and I know most of the rest of the exp.s theres no way I could start a new one now or Id have a massive panic attack and die





on the plus side I wouldnt have to sit the exam.Hmmmmm....

Cherry_Pie

Ok well if it comes up remenber this!!

Crystals disolved in hot water. (10cm portions untill disolved)
Filtered with Buchner
Solution after filtered is boiled, whats left behind is left to dry on clock glass/filter paper.
Et Voilia new pure crystals!
Very very simple and if it comes up you have the gist if you're stuck!

deek

Y'know they should have more "voila"s in other experiments. Makes it a bit more interesting e.g the ethene burned in air et voila luminous flame!!

Cherry_Pie

Ethene burned in what now?? The only ethene exp ik now is the one with AlO3 and ethanol!!!

deek

Ya but then you have to know what ethene burns like,how ethene reacts with bromine water and KMnO4.Its at the end of that exp.

Cherry_Pie

Oh thank god! I read that wrong!! OH ok! I know that thats ok! Phew!!! :eek:

Cherry_Pie

The thress eth exp are ethyne , ethene and ???

deek

Ethene-coulourless gas with sweetish smell

Combustion-Burns with a luminous flame to form carbon dioxide and water (like all organic compounds except haloalkanes which are flame retardants)

Bromine water-Decolourises yellow/red colour of bromine water because of double bond.

KMnO4- decolourises purple colour for the same reason

deek

Theyre characteristic tests at the end of the main experiment to form ethene. Like using tollens reagent to test for ethanal.

colin300

I am so gonna fail it!!
Its actually not even funny!!!!!

Well I could go from 7% in the mocks to about 10% if i know myself.

Quick question my course says c3 or higher in 2 honours then d3 or higher in ordinary irish or english. Can u use honours irish as one of the honours???????

deek

Well not if its ordinary level course

colin300

Its the FT228 Computer science one in DIT level 8???

Cherry_Pie

I would assume so!!

So so scared about chem!!!

Deek ur a gem!!! So ethyne, ethene and ethanal!??? IS that it??
Im just going to find ethanal now and go over it! I know if knew it a while ago!! Does anyone else find they knew this entire course at different points over the last 2 years but when you try to put it all together you've forgotten it all!?

colin300

Ye completely gone new it all well a good bit of it before the exams
then studied every other subject and am offically up the creek!!!

deek

Meant irish couldnt be counted as honours if its ordinary course

colin300

Well anyway going back to do some absolute last minute study and try and cram in as much as possible.

Good luck everyone and we will see how we do on august 17th not that far away now!!



I will be in one major pi**er after this exam if it aint easy for me.

deek

Ya i did a fair bit in chem all year but I knew I had the week off before it (and its my last exam) so I stopped studying it about a week and a half before the start of the leavin. When I went back to it last tuesday Id to start completely from scratch cos Id forgotten it all! :rolleyes:

colin300

ok ye thanks no it was honours irish and honours geography and honours chemistry buut looks like a d3 for me if i am blessed in chemistry it could be a push in geography but we will see!!!

Cherry_Pie

Oh dear god help!!!!!

Richard_Fonzie

Don't go in without knowing how ethanal/ethanoic acid work.

i.e. ethanol (in excess) is oxidised by limited amount of sodium dichromate to ethanal, which is further oxidised by excess sodium dichromate to ethanoic acid.

Ethanal is done with distillation (with ethanol + limited amount of sodium dichromate up top), while ethanoic is done with reflux (ethanol up top, excess sodium dicrhomate in the pear shaped flask).

Generaly:
Primary alcohol > (sodium dichromate) > Aldehyde > (sodium dichromate) > carboxylic acid

and

Secondary alcohol > (hyrdogen + nickel catalyst) > ketone

Two other experiments you should look over in the last few minutes: example of oxidation/reduction reactions experiment, and examples of le chateliers principle experiment. These have lots of different compounds/reactions/colours, so very hard to remember - but easy marks if they come up!

Richard_Fonzie

Oh and Clove Oil has a good chance of coming up. And soap might come up in Section B. The diagrams for each of these will tell you a lot oabout them.

Cherry_Pie

What is the definition of an emulsion!? It came up on my mocks and i can't remenber!!! PLEASE HELP!

Richard_Fonzie

It's where a liquid is suspended in another liquid. E.g. oil (eugenol) spread through water.

edit: the exact definition is "Colloidal suspension of a liquid in a liquid."

But I dont think you need anything that fancy for the leaving cert

Cherry_Pie

Thank u so much!!! I tend to panic if i can't remenber the little things!!!

GOOD LUCK EVERYONE!!!

Richard_Fonzie

Good luck everyone! Finished revising with 50 minutes to go, yay!

Cotsy

If ever i needed you God its now................ please let this be a sweet paper, This is my 7th subject so a D3 will do nicely.
Best of luck all, hopefully we'll manage.

StickyMcGinty

well, what came up??!?!?