**Chemistry...Before/After

Mista

Megan.mcgowan wrote: »

Could someone pleeeease write up a quick summary of the Winkler exp and the chlorine swimming pool one.. My teacher flew through the last few experiments because we were under pressure to finish the course.

Also do you think i'd be okay knowing these topics? (hoping to scrape a C3)
Fuels and Thermochem,
Organic,
Water,
Periodic Table and all that crap.. Radioactivity, trends in p. table, identifying anions,
Most definitions..

Need to revise the exps thinking of just doing the titrations, ethanal/ethanoic acid, volatile liquid and then winkler and the chlorine one cause im running out of time

Any help would be so great!!

Well we have a guaranteed Organic and titration question anyway.


Winkler:
-Rinse out bottle. Removes air bubble/impurities.
-Submerge bottle completely in water to be analysed.
-Use dropper with end under surface of water, add Maganese (II) Sulfate solution. Use another dropper to add alkaline pottasium iodide solution (KI).
-Stopper bottle, shake for half a minute.
-Allow brown ppt to settle until there is a few cm depth of clear liquid at top.
-Use dropper again to add concentrated sulfuric acid.
-Restopper and shake to dissolve ppt.
-Solution should be reddish brown due to liberated iodine.
-Place this solution in conical flask, sodium thiosulfate in burette, titrate as normal.
-End point/indicator is same as iodine/sodium thiosulfate titration.
-In calculation, they usually want p.p.m of 02, this is the same as mg/L.
-Ratio is usaully 1:4

Also, white ppt is formed first before adding acid.
Mn+2 + 2OH- --> Mn(OH)2 ppt (manganese (II) hydroxide)

This reacts with oxygen to form brown ppt.
4Mn(OH)2 + O2 + 2H20 --> 4Mn(OH)3 ppt (manganese (III) hydroxide)

If white ppt does not turn brown, no oxygen in water.

Pepperr

Good summary!.

Naomi00

Pepperr wrote: »

Your book.

Haha, except our book is mostly; 'waffle,waffle,waffle-thing you need to know - waffle, random irrelevant story,waffle', and continue for a few hundred pages.

I can see why they'd want a better version of experiments if their book is as bad as ours, 'Chemistry Live'

Megan.mcgowan

Mista wrote: »

Well we have a guaranteed Organic and titration question anyway.


Winkler:
-Rinse out bottle. Removes air bubble/impurities.
-Submerge bottle completely in water to be analysed.
-Use dropper with end under surface of water, add Maganese (II) Sulfate solution. Use another dropper to add alkaline pottasium iodide solution (KI).
-Stopper bottle, shake for half a minute.
-Allow brown ppt to settle until there is a few cm depth of clear liquid at top.
-Use dropper again to add concentrated sulfuric acid.
-Restopper and shake to dissolve ppt.
-Solution should be reddish brown due to liberated iodine.
-Place this solution in conical flask, sodium thiosulfate in burette, titrate as normal.
-End point/indicator is same as iodine/sodium thiosulfate titration.
-In calculation, they usually want p.p.m of 02, this is the same as mg/L.
-Ratio is usaully 1:4

Also, white ppt is formed first before adding acid.
Mn+2 + 2OH- --> Mn(OH)2 ppt (manganese (II) hydroxide)

This reacts with oxygen to form brown ppt.
4Mn(OH)2 + O2 + 2H20 --> 4Mn(OH)3 ppt (manganese (III) hydroxide)

If white ppt does not turn brown, no oxygen in water.

Thanks thats a big help! Would you defo need to know them wee equations yeah? Im useless at remembering them! :L

Mista

Pepperr wrote: »

Good summary!.

A bit brief, but its all you really need to know.. and that was my revision done for it typing that out :P

Naomi00 wrote: »

Haha, except our book is mostly; 'waffle,waffle,waffle-thing you need to know - waffle, random irrelevant story,waffle', and continue for a few hundred pages.

I can see why they'd want a better version of experiments if their book is as bad as ours, 'Chemistry Live'

We have that as well.. waay to much information, and they even say that the information is irrelevant half the time themselves ("but you dont need to know this for LC level"). I wish I had gotten a revision book

Hayezer

Understanding Chemistry is the worst book I have, doesn't even have an experiments contents page

reznov

Chemistry Live is alright. Some parts of it are atrocious.

Mista

Megan.mcgowan wrote: »

Thanks thats a big help! Would you defo need to know them wee equations yeah? Im useless at remembering them! :L

Nah, proably not. I'd suggest going over the question from the one time it came up, 2005.
http://www.examinations.ie/archive/exampapers/2005/LC022ALPO00EV.pdf
Q1

abbeymate

Hey I was just wondering what experiments do we need to know the equations by heart for? :-S Dire straits now!! Thanks

Hayezer

Lads in organic, how do you tell if a reaction is addition, substitution or elimination?

Mista

abbeymate wrote: »

Hey I was just wondering what experiments do we need to know the equations for?

Test for anions definatley.
Preparation of ethene, ethyne, ethanal, ethanoic acid. Soap.
Oh, and for rates of reaction, know hydrogen peroxide, and a metal in acid. Also, reaction between HCl and Na2S2O3.
Le Chateliers Principle (I think).

In titrations your given them.

Mista

Hayezer wrote: »

Lads in organic, how do you tell if a reaction is addition, substitution or elimination?

If things are added, its addition. Alkenes and alkynes usually undergo this, where a double bond is broken.

Substitution is where things are replaced. Like alkanes added to Cl2 in UV light, to make chloroalkanes.

Elimination is where things are taken out, like a water molecule from ethanol to make ethene.

If you get stuck, draw out the reactant and product and see whats goin on :P

abbeymate

Mista wrote: »

abbeymate wrote: »

Hey I was just wondering what experiments do we need to know the equations for?

Test for anions definatley.
Preparation of ethene, ethyne, ethanal, ethanoic acid. Soap.
Oh, and for rates of reaction, know hydrogen peroxide, and a metal in acid. Also, reaction between HCl and Na2S2O3.
Le Chateliers Principle (I think).

In titrations your given them.

Thanks for your help! Are we given every equation we need for the titrations or do we need to know a few?
Also, what experiments does everyone think will come up this year? B-)

Mista

abbeymate wrote: »

Thanks for your help! Are we given every equation we need for the titrations or do we need to know a few?
Also, what experiments does everyone think will come up this year? B-)

No bother Your given them, or the ratios.. all you need are the ratios :P

My teachers convinced that hydrates sodium carbonate is coming up :P And I think that volatile liquid has a good chance of appearing... hate that one As for organic, maybe ethanal/ethanoic acid.. but I'm going over eveything, not gna do a Plath on chemistry :P

DepoProvera

Mista wrote: »

hydrates sodium carbonate

What is this?

Liveforrugby

Why is sulfuric acid needed in the preparation of ethanal. What's it's function?

Mista

DepoProvera wrote: »

What is this?

Hydrated. My bad :P the water of crystallisation one

abbeymate

Mista wrote: »

abbeymate wrote: »

Thanks for your help! Are we given every equation we need for the titrations or do we need to know a few?
Also, what experiments does everyone think will come up this year? B-)

No bother Your given them, or the ratios.. all you need are the ratios :P

My teachers convinced that hydrates sodium carbonate is coming up :P And I think that volatile liquid has a good chance of appearing... hate that one As for organic, maybe ethanal/ethanoic acid.. but I'm going over eveything, not gna do a Plath on chemistry :P

Yeah, I really agree with you!! It's exactly what I was thinking, well what my was teacher thinking :-P Well I was lucky with kavanagh.. NO must study EVERYTHING! :L

DepoProvera

Liveforrugby wrote: »

Why is sulfuric acid needed in the preparation of ethanal. What's it's function?

Supplies H+ ions for oxidation afaik.. Not sure though!

Hayezer

Mista wrote: »

If things are added, its addition. Alkenes and alkynes usually undergo this, where a double bond is broken.

Substitution is where things are replaced. Like alkanes added to Cl2 in UV light, to make chloroalkanes.

Elimination is where things are taken out, like a water molecule from ethanol to make ethene.

If you get stuck, draw out the reactant and product and see whats goin on :P

Thanks a mill !

DepoProvera

Mista wrote: »

Hydrated. My bad :P the water of crystallisation one

You scared me there.. Yeah I hope that comes up

Liveforrugby

Mista wrote: »

No bother Your given them, or the ratios.. all you need are the ratios :P

My teachers convinced that hydrates sodium carbonate is coming up :P And I think that volatile liquid has a good chance of appearing... hate that one As for organic, maybe ethanal/ethanoic acid.. but I'm going over eveything, not gna do a Plath on chemistry :P

Ahh c'mon. Where's the fun when you have everything learnt off? Where's the risk? You might as well say no to life then if you're going to be like that

Saracarroll

Liveforrugby wrote: »

Why is sulfuric acid needed in the preparation of ethanal. What's it's function?

To supply H+'s

3(c2h5oh) + (cr2o7)2- + 8h+ = 3(ch3cho) + 2(cr3+) + 7(h20)

Mista

Hayezer wrote: »

Thanks a mill !

No bother

DepoProvera wrote: »

You scared me there.. Yeah I hope that comes up

Me to I've finally learned how to find x!

Liveforrugby wrote: »

Ahh c'mon. Where's the fun when you have everything learnt off? Where's the risk? You might as well say no to life then if you're going to be like that

Haha, ah I fecked up one subject, not gna do that on another :P Besides, I love chemistry

Hayezer

Let's say with an ester like methyl ethanoate, is methanol the alcohol and ethanoic acid the carb. acid? Or is it the other way around ?

DepoProvera

Hayezer wrote: »

Let's say with an ester like methyl ethanoate, is methanol the alcohol and ethanoic acid the carb. acid? Or is it the other way around ?

Yep that's right. It helps if you draw it out you can see the carboxylic acid in the structure.

paddyhes

Hayezer wrote: »

Let's say with an ester like methyl ethanoate, is methanol the alcohol and ethanoic acid the carb. acid? Or is it the other way around ?

Yep that's it.
Alcohol makes up the first part.
Carb. acid makes up the second.

TheHazer

Naomi00 wrote: »

I can see why they'd want a better version of experiments if their book is as bad as ours, 'Chemistry Live'

That's written by the same man who makes out the chemistry test every year :rolleyes:

ivanh

We don't need to know the equations for soap, ethanal or ethanoic acid

ivanh

Liveforrugby wrote: »

Why is sulfuric acid needed in the preparation of ethanal. What's it's function?

Provides H+ ions for the reaction!

DepoProvera

ivanh wrote: »

We don't need to know the equations for soap, ethanal or ethanoic acid

We do need to know soap equation.. They asked half of it before.

Mista

ivanh wrote: »

We don't need to know the equations for soap, ethanal or ethanoic acid

We definitely do for soap.

ivanh

Anyone not know the scientists and what they discovered in Chapter 1?

I just can't get them into my head, but I've an awful feeling they'll be a big chunk of Q5 or at least a part of Q4..

Can anyone summarise them for me? It would be greatly appreciated

reznov

Know all equations if you want an A1.
Don't expect an A1 if you haven't every page memorised.

ivanh

Mista wrote: »

We definitely do for soap.

Oh yeah sorry my bad, but the other two, definitely not

DepoProvera

ivanh wrote: »

Anyone not know the scientists and what they discovered in Chapter 1?

I just can't get them into my head, but I've an awful feeling they'll be a big chunk of Q5 or at least a part of Q4..

Can anyone summarise them for me? It would be greatly appreciated

I doubt they'll come in in Q5! Came up last two years. I'd say its trends and bonding(first ionisations is my bet). Definitely for Q4 though :P

Mista

ivanh wrote: »

Oh yeah sorry my bad, but the other two, definitely not

No bother And yea, only realised that now you've mentioned it.. thank god for small mercies anyway!

Spattersonox

I need a B2... FCUK

reznov

ivanh wrote: »

Oh yeah sorry my bad, but the other two, definitely not

If you want a B1, don't memorise the other two.

DepoProvera

reznov wrote: »

If you want a B1, don't memorise the other two.

Bold Reznov!

reznov

DepoProvera wrote: »

Bold Reznov!

Only the top students achieve an A1.
The top students practically have university level knowledge coming into the exam.
Best way to see if you're capable is to sit a university chemistry exam (3rd year recommended). If you achieve a high grade, you're ready for the leaving.

ivanh

reznov wrote: »

If you want a B1, don't memorise the other two.

What are you on about?

earwax_man

I just have to look over definitions and experiments again, and I'm all set. These are all of them that have been asked since 2002.

Page one
Page two

Spattersonox

earwax_man wrote: »

I just have to look over definitions and experiments again, and I'm all set. These are all of them that have been asked since 2002.

Page one
Page two

Legend!

DepoProvera

earwax_man wrote: »

I just have to look over definitions and experiments again, and I'm all set. These are all of them that have been asked since 2002.

Page one
Page two

Hmm you have nice writing

Coeurdepirate

Lads, all I know is equilibrium and fuels & heats if i manage to get the rest of organic, water, oxidation/reduction, some atomic theory and the organic experiments and titrations done by tomorrow, should I pass honours? Like I'd be happy with a D3.

ei.sderob

reznov wrote: »

Only the top students achieve an A1.
The top students practically have university level knowledge coming into the exam.
Best way to see if you're capable is to sit a university chemistry exam (3rd year recommended). If you achieve a high grade, you're ready for the leaving.

Are you alright? Mentally that is.

ashalingable

ei.sderob wrote: »

Are you alright? Mentally that is.

Seconded!

ei.sderob

Anyone have the definition for a covalent bond and a sublevel? Grand for the rest on those links.

HeaneyBabe

Coeurdepirate wrote: »

Lads, all I know is equilibrium and fuels & heats if i manage to get the rest of organic, water, oxidation/reduction, some atomic theory and the organic experiments and titrations done by tomorrow, should I pass honours? Like I'd be happy with a D3.

Yeah just make sure you know all your organic experiments because they could ask anything on organic