***2013 LC Chemistry Before/After***

Nl90

Can any one explain to me please what are the figures to be taken in V Analysis ? I always feel lost cause I missed that at school and just started studying !:/

MarieCurie22

simons545 wrote: »

I presume you're referencing the experiment with the dichromate salts we can't do. I'm not 100% sure if that would be acceptable because an acidic oxide, like Sulphur dioxide will neutralise a base the same way an acid will, but to the extend of my knowledge is not an acid itself until in solution.
If I was doing that question I would write out the reaction equation for its reaction with Na2CO3 or CaCO3 and then explain why carboxylic acids are acids. They lose a H+ due to the stability of the carboxylate ion, (C=OO-), and form an area of electronegativity.
I presume if you wrote down the reaction equation and that, because CO2 is evolved/produced in the reaction along with a salt and water, it could be classed as a neutralisation reaction.
Here's the reaction equation for the Na2CO3:
2CH3COOH+Na2CO3-->2CH3COONa+CO2+H20

and the CaCO3:
2CH3COOH+CaCO3-->(CH3COO)2Ca+CO2+H20

hope this helped somewhat

Thats what I was asking in laymans terms...:P thanks yup i was gonna do the equation just easier to remember limestone :P

MarieCurie22

Nl90 wrote: »

Can any one explain to me please what are the figures to be taken in V Analysis ? I always feel lost cause I missed that at school and just started studying !:/

If you're on about V1 M1 N1 etc?
Ok so draw a quick sketch about whats above and below..
Let 1 = Whats in the burette (usually always the acid)
V1 = the volume of acid needed for the reaction to finish this is given in the wordy bits at the start.
M1= The molarity of the acid used usually given if not let this = x
N1 = The number in front of the acid in the balanced equation.


Let 2 = The substance in the conical flask usually the base.
V2= The volume of base used this is always a fixed value and will also be given.
M2= The molarity (moles/litre) of the base may be given if not let this = x
N2= The moles ie the number in front of the base in the balanced equation...

Then you can use the formula: (v1 x M1)/N1 = (v2 x M2)/N2 to find the missing value.

Please feel free to Private message me if youd like help I love helping others with cham and it helps me learn in the process

simons545

Does anyone have a few points on Dalton's Atomic Theory for me please? don't have any points in my book on it and it has come up a few times.
I know that one of them is atoms are small indivisible particles...that's it.
Thanks in advance

MarieCurie22

simons545 wrote: »

Does anyone have a few points on Dalton's Atomic Theory for me please? don't have any points in my book on it and it has come up a few times.
I know that one of them is atoms are small indivisible particles...that's it.
Thanks in advance

I have a stupid rhyme....
"It all started with the greeks then Dalton...
He said atoms were indivisble...
Uncreatable...
All things are made of 'em" Its meant to be sung....

Anyways
He said...
-Atoms cannot be created or destroyed (Wrong)
-Atoms were indivisible (smallest particle in nature) (Proved wrong also)
-All matter is made of particles (only thing he got right!)

Bionicle

I would advise anyone doing this exam to look at the syllabus to see what exactly must be known. It is the best study guide you will find as it will clearly tell you what is needed. I did this and got 397/400 last year. It definitely helped me make less mistakes. It can be found here:

http://www.curriculumonline.ie/uploadedfiles/PDF/lc_chemistry_sy.pdf

I advise that you guys try do all experiments. It gives you so much more option in the long questions and is a massive relief midthrough in the exam knowing you have somuch choice. If you have time, learn the option. It is handy marks and will help with q4 as well.

simons545

MarieCurie22 wrote: »

I have a stupid rhyme....
"It all started with the greeks then Dalton...
He said atoms were indivisble...
Uncreatable...
All things are made of 'em" Its meant to be sung....

Anyways
He said...
-Atoms cannot be created or destroyed (Wrong)
-Atoms were indivisible (smallest particle in nature) (Proved wrong also)
-All matter is made of particles (only thing he got right!)

Hahaha thanks think they've updated conservation of mass to "during the course of a chemical reaction" so they don't take into account nuclear reactions anymore. Thanks though I appreciate it:)

MarieCurie22

simons545 wrote: »

Hahaha thanks think they've updated conservation of mass to "during the course of a chemical reaction" so they don't take into account nuclear reactions anymore. Thanks though I appreciate it:)

Yes but thats exactly what Dalton said so :P thats what you gotta give no matter what the relevance aujourd'hui :P

mocker2012

what were the 3 marks lost for?

Bionicle

mocker2012 wrote: »

what were the 3 marks lost for?

I actually had three questions on 47/50 and one on 45/50. I lost 3 marks for the reason as to why a pipette filler was used in Q1 because they didn't think 'accuracy and to provide suction' was a good answer. I lost 3 in Q5 when they asked what property is affected by the presence of hydrogen bonds and I misread it as what property affects the presence of hydrogen bonds, which annoyed me because EVERYONE knows its boiling point *facepalm*. I lost 3 marks for my graph in the rates of reaction question and lost 5 in the water question about how water is deionsed or something even though I wrote a page bout it which did have the stuff in the marking scheme but they didn'taccept it. :S

mocker2012

Bionicle wrote: »

I actually had three questions on 47/50 and one on 45/50. I lost 3 marks for the reason as to why a pipette filler was used in Q1 because they didn't think 'accuracy and to provide suction' was a good answer. I lost 3 in Q5 when they asked what property is affected by the presence of hydrogen bonds and I misread it as what property affects the presence of hydrogen bonds, which annoyed me because EVERYONE knows its boiling point *facepalm*. I lost 3 marks for my graph in the rates of reaction question and lost 5 in the water question about how water is deionsed or something even though I wrote a page bout it which did have the stuff in the marking scheme but they didn'taccept it. :S

Pesky markers!! I only asked because I did the LC last year without chemistry and I decided to do it this year. I came close to the elusive 100% in ag.science, but was randomly re-checked and brought me back to 98%.:cool: I know its irrelevant but the markers are sly enough.:P Anyway since I'm only doing chemistry now i feel like 400 marks is my goal!! :rolleyes:

mocker2012

By the way, are you in uni this year or gap year? If so, what are you studying, I'm racking my brains trying to choose between ucd science or engineering.

Bionicle

I'm in uni doing maths in tcd.

outnumbered

What's the difference between the chapters, Electrochemistry and Elecrtonegativity? I realised I do not have a chapter on electronegativity! Has anyone any of the main stuff I need to know? This is scaring me now!

Hamza Malik

outnumbered wrote: »

What's the difference between the chapters, Electrochemistry and Elecrtonegativity? I realised I do not have a chapter on electronegativity! Has anyone any of the main stuff I need to know? This is scaring me now!

Electrochemistry is basically using electricity to bring about chemical reactions. There's a small experiment in it which is very easy to learn. It appears as part of a question in Q11

Electronegativity is the force of attraction between shared paired of electrons in a covalent bond. It comes up in Q5

MarieCurie22

outnumbered wrote: »

What's the difference between the chapters, Electrochemistry and Elecrtonegativity? I realised I do not have a chapter on electronegativity! Has anyone any of the main stuff I need to know? This is scaring me now!

Electronegativity isnt a chapter nor does it have anything to do with electrochemistry in reality it would be in the section of boding....dealing with ionic an covalent bonds if you have chemistry live its in the chapter with the benzoic acid experiment (Dont have book atm)

outnumbered

Thanks Guys,
we don't have a book, just notes so I was worried. So basically electronegativity is just a definition?

ray2012

outnumbered wrote: »

Thanks Guys,
we don't have a book, just notes so I was worried. So basically electronegativity is just a definition?

Yes, electronegativity is the relative attraction that an atom has for a shared pair of electrons in a covalent bond.

Hamza Malik

outnumbered wrote: »

Thanks Guys,
we don't have a book, just notes so I was worried. So basically electronegativity is just a definition?

Yeah but you need to know the trends of electronegativity across and down the periodic table :rolleyes:

ray2012

Just in-case anyone doesn't know (I only saw it AFTER my mocks), the increase/decrease of ionisation energies/electronegativity values are given in the log tables. They give you a periodic table and the electronegativity/ionisation energies are given, so you can easily see if it increases/decreases across a period or whatever. As I said, I only noticed this after my mocks, and I was left learning off whether they increase/decrease. But now I only have to know why, makes it a fair bit simpler to be honest! :P

I'm sure most of ye know this, but just in-case I thought I'd post it! :pac:

Acciaccatura

And don't forget, atomic radius is the opposite to electronegativity and increases down a group due to electrons entering a new shell and decreases across a period due to increased nuclear charge. Just felt it was missing, after talking about ionisation energy and electronegativity :P

MarieCurie22

Acciaccatura wrote: »

And don't forget, atomic radius is the opposite to electronegativity and increases down a group due to electrons entering a new shell and decreases across a period due to increased nuclear charge. Just felt it was missing, after talking about ionisation energy and electronegativity :P

Just think of this:


Hat represents the atomic radius....gets smaller across....
His robe represents the atomic radius going down...it gets bigger/wider

Prodigious

Still waiting with baited breath for this song

Acciaccatura

You missed it, I posted it yesterday, Prodge! :P

Acciaccatura wrote: »

Here it is! I'm not gonna lie, I am quite embarrassed about this :pac: I'll just leave all my shame with this post :P

NB: Mods should note that I'm not a regular Youtuber looking for attention and subscribers. I'm far too mediocre for that crap :P

Prodigious

Acciaccatura wrote: »

You missed it, I posted it yesterday, Prodge! :P

Jaysus, some job! Beautiful voice, well done

Acciaccatura

Prodigious wrote: »

Jaysus, some job! Beautiful voice, well done

What planet are you on?! :P Sure twas only for the laugh anyway, but still, I sang those definitions off the top of my head But thank you, glad you like it

olazbabes

I think it is the most impossible subject in LC. you are all talented I left the Chem section blank in JC. good luck

Nl90

Thanks MarieCurie22 (F)

I thought of posting some random Qs to help us revise


1- what affect will have adding a catalyst on the yield of hydrogen in steam reforming of natural gas ?

2- give a visual evidence on the Intermediate Formation theory ?

3- why carboxylic acids act as acids ?

outnumbered

Nl90 wrote: »

Thanks MarieCurie22 (F)

I thought of posting some random Qs to help us revise


1- what affect will have adding a catalyst on the yield of hydrogen in steam reforming of natural gas ?

2- give a visual evidence on the Intermediate Formation theory ?

3- why carboxylic acids act as acids ?

1. Speed it up
2. Iodine snake
3.?
They are tough questions haha

meleanor

outnumbered wrote: »

1. Speed it up
2. Iodine snake
3.?
They are tough questions haha

1. No effect (equilibrium)
2. The green colour formed in the potassium tartrate experiment?
3. They form stable ions and because of the polarity of the O-H bond?