* Chemistry * Predictions / discussion / aftermath * (1 thread please)

partyatmygaff

I'd say one of the two oxidation of Ethanol experiments will come up this year. The reason behind that is that the Dept. Education have banned the use of hexavalent chromium in secondary schools so we'll be the last year to have actually done those two experiments. That and the equilibrium experiment involving Cobalt Chloride and a Dichromate salt. That experiment contains two banned chemicals.

Joseph...

what experinments do ye think will come up??

ClaireMarie

My teacher has really been predicting bleach and ethanal for the first too!
Bleach especially - as it has never been up.
If winkler and benzoic acid come up for Q 1 and 2 - SOMEONE. WILL. PAY.
Lol, I had a good teacher - but for some reason I just hate those 2!

Phareon

Joseph... wrote: »

what experinments do ye think will come up??

Our teacher's tipping Bleach titration and Rates of Reaction, i.e NaOH and HCl !!
All of the Organic experiments have come up before, so just go over Exam Papers!!!
And like the previous poster said, the ones with banned chemicals are likely!!

._.

I'll cry if ethanal comes up, I really can't do that calculation.

DM360

partyatmygaff wrote: »

Where in the Chemistry course do you need to work with ratios like these?

Empirical formula questions have numbers and ratios like that.

Preparation for ethanal or ethanoic acid or possibly a question with both for the Organic Chemistry Exp.

Volatile liquid or heat of neutralisation for the other I've been told.

And another acronym: OPRN (remember that how you will ) for electrochemistry. Oxidation is at Positive Electrode, Reduction at Negative

._.

ok, does anybody else actually have this godforsaken Chemistry Revise Wise book?
Page 99/100, does how they got to 1 mole of MgO = 40g make sense to anybody? They literally just wrote it down and gave absolutely no explanation as to how they got there..

epicwinning

._. wrote: »

ok, does anybody else actually have this godforsaken Chemistry Revise Wise book?
Page 99/100, does how they got to 1 mole of MgO = 40g make sense to anybody? They literally just wrote it down and gave absolutely no explanation as to how they got there..

mass (in grams) = MR(n)

n = 1 , MR = 16+24 = 40

m = 40*1
m = 40g

Phareon

._. wrote: »

ok, does anybody else actually have this godforsaken Chemistry Revise Wise book?
Page 99/100, does how they got to 1 mole of MgO = 40g make sense to anybody? They literally just wrote it down and gave absolutely no explanation as to how they got there..

Mr of Oxygen is 16, so 1 mole O = 16g,
Mr of Magnesium is 24, so 1 mole Mg = 24g
24g + 16g = 40g

^^ Ninja'd

Exothermic

._. wrote: »

ok, does anybody else actually have this godforsaken Chemistry Revise Wise book?
Page 99/100, does how they got to 1 mole of MgO = 40g make sense to anybody? They literally just wrote it down and gave absolutely no explanation as to how they got there..

Go to your periodic table Mg = 24 O = 16. Add 'em up, you get 40. Hence, MgO = 40g.

Exothermic

Whoops. :P Well, that question certainly got answered.

._.

grrrrr, is it too much to ask for them to actually tell you where they're pulling these numbers from?

Thanks guys, chemistry calculations are really not my thing.

epicwinning

:P

And yeah, I have the Revise-Wise Chemistry. It's just a smaller version of the Chemistry book we used (Understanding Chemistry, I think it was called...) for the last couple of years.

ride-the-spiral

partyatmygaff wrote: »

Where in the Chemistry course do you need to work with ratios like these?

AFAIK, the only time you ever need to manipulate ratios is in Stoichiometry in the limiting reagent calculations and they're never going to be in ratios that large.

Empirical formula most likely

_coley_

Could anyone explain to me in simple terms how to balance a redox equation thing with the oxidation numbers?
Teachers a dud

River Song

_coley_ wrote: »

Could anyone explain to me in simple terms how to balance a redox equation thing with the oxidation numbers?
Teachers a dud

I'll do out one very quickly if you want?

YodaBoy

Anyone have tips for the experiments they could throw into section 2?? Maybe equilibrium ones??? Dont know those ones at all

River Song

Okay, did 2002 balencing REDOX equations Question:

stealinhorses

Awesome whiteboard.

River Song

stealinhorses wrote: »

Awesome whiteboard.

Reads, of Nassau St., like 15 Euro.

macskanadrag

DM360 wrote: »

And another acronym: OPRN (remember that how you will ) for electrochemistry. Oxidation is at Positive Electrode, Reduction at Negative

Modified acronym:
Positive
Oxidation
Reduction
Negative

Slightly easier to remember

macskanadrag

Michael_E wrote: »

Reads, of Nassau St., like 15 Euro.

Fair play

Is there a need to cross multiply?
I'd do just the balancing (-> 4H2O, 8H+, 2Cl-) and check if the numbers are correct, ie. add them up on both sides and make sure they are equal - done. So i wouldn't end up with 5 Cl2 and 10 Cl-...

Just one thing - make sure that you write the oxidation number PER ATOM under the thing, ie put -2 under O4 and not -8. I read this in a few places.

EmacB

Anybody have a list of experiments that can come up for question 3?

Or even just the ones havent havent yet come up?

Gavarn

I'm hoping to god the experiments are like this:

Q1. Bleach
Q2. Ethanal
Q3. Volatile liquid or formation O2 and Hydrogen from Hydrogen Peroxide.

I think that it is pretty likely it will be similar to this, however, I have to study them all to be sure

DM360

macskanadrag wrote: »

Modified acronym:
Positive
Oxidation
Reduction
Negative

Slightly easier to remember

Wow, amazing, never saw that, I wasn't trying to be discrete :P

Exothermic

For the titrations: bleach, water of crystallisation, Winkler. But don't completely neglect the others as an iron one or iodine-thiosulphate is also possible.
Organic: ethanal, ethanoic acid, clove oil.
Q3: Large number of possibilities. Volatile liquid, heat of reaction (polystyrene cup), rates of reaction. What else?

Any predictions for what will be big on the paper? Gosh, really need to get my head down today and get studying.

partyatmygaff

Can an equilibrium experiment come up as an experiment question I.e. Q1-3? Either way i'm almost certain we'll be getting a question on one of the experiments with banned chemicals.

ClaireMarie

partyatmygaff wrote: »

Can an equilibrium experiment come up as an experiment question I.e. Q1-3? Either way i'm almost certain we'll be getting a question on one of the experiments with banned chemicals.

Yep - they can come up as Q3

Gavarn

Exothermic wrote: »

For the titrations: bleach, water of crystallisation, Winkler. But don't completely neglect the others as an iron one or iodine-thiosulphate is also possible.
Organic: ethanal, ethanoic acid, clove oil.
Q3: Large number of possibilities. Volatile liquid, heat of reaction (polystyrene cup), rates of reaction. What else?

Any predictions for what will be big on the paper? Gosh, really need to get my head down today and get studying.

I think Rates of Reaction will be up in the non-experiment part of the paper as it was an experiment last year (the effect of concentration and temperature).

_coley_

Michael_E wrote: »

Okay, did 2002 balencing REDOX equations Question:

Thanks Soooo Much
Much easier now (: