**Chemistry...Before/After

paddyhes

Coeurdepirate wrote: »

Thank you so much!

No problem (y).

Hayezer

Please give us nice experiments and nice equilibrium question! Question like 2005 equilibrium would ruin my day

Pepperr

Hayezer wrote: »

Please give us nice experiments and nice equilibrium question! Question like 2005 equilibrium would ruin my day

They took the practical experiment of that question off out course recently, but apparently we are supposed to still know the theory..

I think it would be really unfair and unlikely that it comes up, don't worry about it

reznov

Should I know the Winkler equations? Any point of learning them?

Hayezer

Bitta Haber Bosch with right conditions etc would go down nicely :pac:

reznov

Pepperr wrote: »

It's similar to the ethanal one, except you have excess acidified dichromate and you don't distil off the product.

You set it up in reflux, making sure oxidising agent (Dichromate) is in excess.
The Orange dichromate turns green as the ethanol oxidises.

The set up starts with ethanol and water in a dripping funnel, dripping through a liebig condenser into a pear shaped flask. The flask is in a water bath, and in the flask is the dichromate, dilute sulfuric acid and anti bumping granules. After 30 mins, you are done! (Might have missed something, that is most of it though.)

MAKE SURE THE DICHROMATE IS IN THE PEAR FLASK. This is to ensure complete oxidation to Ethanoic Acid. REMEMBER THE TESTS to prove that Ethanoic acid is indeed a weak acid. Just test adding NaOH, Mg Metal and Sodium Carbonate.

drbtrenier

Preparation
1. Ethanol and water in tap funnel, added drop by drop down a condenser to sodium dichromate and sulfuric acid in pear-shaped flask. (Flask has anti-bumping chips in it.)
2. This reaction is very exothermic so:
-Only add drop by drop
-Wait for the reaction to subside before adding next few drops
-Immerse the flask in a beaker of cold water.
3. Reflux this mixture for about 20 mins.
4. Colour changes from orange to green as Cr(VI) is reduced to Cr(III). Remember that sodium dichromate is the oxidising agent for the reaction.
5. Rearrange the apparatus for distillation over a bunsen burner. BB very important as ethanoic acid has a boiling pt of 118 C.

Properties
These are basically just reactions as acids.
1. Reacts with sodium hydroxide (base) to form a salt and water:
CH3COOH + NaOH -> CH3COONa + H2O
During this process phenophthalein changes from colourless to pink.

2. Reacts with sodium carbonate to form a salt, carbon dioxide and water. Fizzing is observed:
2CH3COOH + Na2CO3 -> 2CH3COONa + CO2 + H2O

3. Reacts with magnesium metal to form a salt (magnesium ethanoate) and hydrogen gas. Burns with a pop noise:
2CH3COOH + Mg -> (CH3COO)2Mg + H2

Hope this helps...

EDIT: **Sodium dichromate in excess to ensure complete oxidation to ethanoic acid**

Hayezer

drbtrenier wrote: »

Preparation
1. Ethanol and water in tap funnel, added drop by drop down a condenser to sodium dichromate and sulfuric acid in pear-shaped flask. (Flask has anti-bumping chips in it.)
2. This reaction is very exothermic so:
-Only add drop by drop
-Wait for the reaction to subside before adding next few drops
-Immerse the flask in a beaker of cold water.
3. Reflux this mixture for about 20 mins.
4. Colour changes from orange to green as Cr(VI) is reduced to Cr(III). Remember that sodium dichromate is the oxidising agent for the reaction.
5. Rearrange the apparatus for distillation over a bunsen burner. BB very important as ethanoic acid has a boiling pt of 118 C.

Properties
These are basically just reactions as acids.
1. Reacts with sodium hydroxide (base) to form a salt and water:
CH3COOH + NaOH -> CH3COONa + H2O
During this process phenophthalein changes from colourless to pink.

2. Reacts with sodium carbonate to form a salt, carbon dioxide and water. Fizzing is observed:
2CH3COOH + Na2CO3 -> 2CH3COONa + CO2 + H2O

3. Reacts with magnesium metal to form a salt (magnesium ethanoate) and hydrogen gas. Burns with a pop noise:
2CH3COOH + Mg -> (CH3COO)2Mg + H2

Hope this helps...

Thats great thanks! Do we need those equations ? And I thought the salt formed is ethyl ethanoate?

paddyhes

Hayezer wrote: »

Thats great thanks! Do we need those equations ? And I thought the salt formed is ethyl ethanoate?

Nope ethyl ethanoate is an ester formed by combining ethanol with ethanoic acid.

drbtrenier

Hayezer wrote: »

Thats great thanks! Do we need those equations ? And I thought the salt formed is ethyl ethanoate?

Yes, I think so, but they're fairly easy, just think of how an acid works, gets rid of a proton, salt is formed when reacts with a base.

2nd answer, no, ethyl ethanoate is an ester, be careful with that! It's formed when a carboxylic acid reacts with an alcohol.

ChemHickey

Hayezer wrote: »

drbtrenier wrote: »

Preparation
1. Ethanol and water in tap funnel, added drop by drop down a condenser to sodium dichromate and sulfuric acid in pear-shaped flask. (Flask has anti-bumping chips in it.)
2. This reaction is very exothermic so:
-Only add drop by drop
-Wait for the reaction to subside before adding next few drops
-Immerse the flask in a beaker of cold water.
3. Reflux this mixture for about 20 mins.
4. Colour changes from orange to green as Cr(VI) is reduced to Cr(III). Remember that sodium dichromate is the oxidising agent for the reaction.
5. Rearrange the apparatus for distillation over a bunsen burner. BB very important as ethanoic acid has a boiling pt of 118 C.

Properties
These are basically just reactions as acids.
1. Reacts with sodium hydroxide (base) to form a salt and water:
CH3COOH + NaOH -> CH3COONa + H2O
During this process phenophthalein changes from colourless to pink.

2. Reacts with sodium carbonate to form a salt, carbon dioxide and water. Fizzing is observed:
2CH3COOH + Na2CO3 -> 2CH3COONa + CO2 + H2O

3. Reacts with magnesium metal to form a salt (magnesium ethanoate) and hydrogen gas. Burns with a pop noise:
2CH3COOH + Mg -> (CH3COO)2Mg + H2

Hope this helps...

Thats great thanks! Do we need those equations ? And I thought the salt formed is ethyl ethanoate?

Ethyl ethanoate is the ester.

reznov

ChemHickey wrote: »

Ethyl ethanoate is the ester.

Yeah the salt sodium ethanoate forms.

Hey Chem, do we need the winkler ewuations learned off?

Hayezer

Dunno where I got that from :pac: thanks, will remember it noww

ChemHickey

reznov wrote: »

ChemHickey wrote: »

Ethyl ethanoate is the ester.

Yeah the salt sodium ethanoate forms.

Hey Chem, do we need the winkler ewuations learned off?

Not specified, but if you have time, I would as he has to find a place to pull marks off people! They'll be the first thing I'll write down if it's on for q1!

Hermione Granger

drbtrenier wrote: »

Preparation
1. Ethanol and water in tap funnel, added drop by drop down a condenser to sodium dichromate and sulfuric acid in pear-shaped flask. (Flask has anti-bumping chips in it.)
2. This reaction is very exothermic so:
-Only add drop by drop
-Wait for the reaction to subside before adding next few drops
-Immerse the flask in a beaker of cold water.
3. Reflux this mixture for about 20 mins.
4. Colour changes from orange to green as Cr(VI) is reduced to Cr(III). Remember that sodium dichromate is the oxidising agent for the reaction.
5. Rearrange the apparatus for distillation over a bunsen burner. BB very important as ethanoic acid has a boiling pt of 118 C.

Properties
These are basically just reactions as acids.
1. Reacts with sodium hydroxide (base) to form a salt and water:
CH3COOH + NaOH -> CH3COONa + H2O
During this process phenophthalein changes from colourless to pink.

2. Reacts with sodium carbonate to form a salt, carbon dioxide and water. Fizzing is observed:
2CH3COOH + Na2CO3 -> 2CH3COONa + CO2 + H2O

3. Reacts with magnesium metal to form a salt (magnesium ethanoate) and hydrogen gas. Burns with a pop noise:
2CH3COOH + Mg -> (CH3COO)2Mg + H2

Hope this helps...

EDIT: **Sodium dichromate in excess to ensure complete oxidation to ethanoic acid**

I thought this couldn't come up due to the dichromate being carcinogenic ???

ivanh

Anyone think that the redox titration between Potassium Permanganate and Ammonium Iron (II) Sulfate might come up in Q1?

I don't think it's ever been asked?

Hermione Granger

ivanh wrote: »

Anyone think that the redox titration between Potassium Permanganate and Ammonium Iron (II) Sulfate might come up in Q1?

I don't think it's ever been asked?

I doubt it because there's not much to ask..:P

reznov

Hermione Granger wrote: »

I thought this couldn't come up due to the dichromate being carcinogenic ???

It can! Most schools prepared the experiment already. But maybe they will leave it out. Hopefully not

Mista

reznov wrote: »

It can! Most schools prepared the experiment already. But maybe they will leave it out. Hopefully not

We did it in Maynooth as a demonstration

Also, I just came across a Halogen experiment to do with demonstrating oxidation.. would it be worth my while looking over it?

ChemHickey

ivanh wrote: »

Anyone think that the redox titration between Potassium Permanganate and Ammonium Iron (II) Sulfate might come up in Q1?

I don't think it's ever been asked?

I've a feeling they'll make a water of crystallisation out of it.

ChemHickey

Mista wrote: »

reznov wrote: »

It can! Most schools prepared the experiment already. But maybe they will leave it out. Hopefully not

We did it in Maynooth as a demonstration

Also, I just came across a Halogen experiment to do with demonstrating oxidation.. would it be worth my while looking over it?

Yes.

drbtrenier

Hermione Granger wrote: »

I thought this couldn't come up due to the dichromate being carcinogenic ???

It still can, check out this article... We're still expected to know the "theoretical knowledge" :pac:

http://www.independent.ie/lifestyle/education/school-science-labs-told-to-stop-using-blacklisted-chemicals-2585586.html

DepoProvera

ChemHickey wrote: »

I've a feeling they'll make a water of crystallisation out of it.

My practical teacher was of the same opinion.

Hermione Granger

Im thinking water of crystallistion and volatile liquid q3 any ideas for q 2 .

Technically it says in the syllabus that question 1 2 and 3 cannot be demonstrations they have to be done by the students but ethanal and ethanoic acid can be asked in Section B;)

ivanh

reznov wrote: »

It can! Most schools prepared the experiment already. But maybe they will leave it out. Hopefully not

We did both the ethanal/ethanoic expts.

Still standing! For now.....

(They were fun too)

reznov

Hermione Granger wrote: »

Im thinking water of crystallistion and volatile liquid q3 any ideas for q 2 .

Technically it says in the syllabus that question 1 2 and 3 cannot be demonstrations they have to be done by the students but ethanal and ethanoic acid can be asked in Section B;)

Prep of Ethene. :pac:

Mista

reznov wrote: »

Prep of Ethene. :pac:

Hopefully.. and mix in some ethyne as well :pac:

ivanh

drbtrenier wrote: »

It still can, check out this article... We're still expected to know the "theoretical knowledge" :pac:

http://www.independent.ie/lifestyle/education/school-science-labs-told-to-stop-using-blacklisted-chemicals-2585586.html

Well that new syllabus is gonna suck monkey balls

Those experiments were the best part!

As Declan Kennedy said himself: "There are fun times ahead!"

Lol

Hermione Granger

Here's hoping for a lovely leaving cert chemistry paper in 2012 in approx 1 hour 48 minutes time with water of crystallistaion preparation of ethene and ethyne and volatile liquid

Hayezer

Hermione Granger wrote: »

Here's hoping for a lovely leaving cert chemistry paper in 2012 in approx 1 hour 48 minutes time with water of crystallistaion preparation of ethene and ethyne and volatile liquid

That would be so good Or the rates of reaction one, lovely experiment :P! Wouldn't mind winkler, ethanal or ethanoic either!