***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?

outnumbered

meleanor wrote: »

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?

OOOOPS better go over rates :P

meleanor

outnumbered wrote: »

OOOOPS better go over rates :P

Meh I'm rusty too, it's the potassium sodium tartrate + cobalt(ll) salt + h2O2 experiment! :P

outnumbered

meleanor wrote: »

Meh I'm rusty too, it's the potassium sodium tartrate + cobalt(ll) salt + h2O2 experiment! :P

Ah thanks. I am hoping that there wont be too much on rates this year. I am good at equilibrium so here's hoping!!!

weirdspider

outnumbered wrote: »

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

Its the inductive effect and the stability of the carboxylate ion

meleanor

outnumbered wrote: »

Ah thanks. I am hoping that there wont be too much on rates this year. I am good at equilibrium so here's hoping!!!

I totally understand equilibrium, yet something always seems to go wrong, so I'm avoiding it, I'll do every other Q :P

ClassicsStuff

Cba going through all the thread so will someone give me some predictions please! I almost failed my mocks and I'm aiming for a C1/B3 help would be appreciated!

0mega

Just looking through the syllabus, I'll pull out the hard qs:

Distinction between chemical reaction and nuclear reaction?

Example of a displacement reaction in the electrochemical series?

What is a transition element and give examples?

Uses of helium and argon related to their chemical unreactivity?

Physical properties of ionic/covalent substances?

Relationship between symmetry and polarity in a molecule?

Oxidation number of oxygen in H202

Reasons why real gases deviate from ideal gas behaviour?

Composition of LPG?

What does MTBE stand for?

What is the surface adsorption theory?

What is a primary alcohol?

Use of propanone and propanoic acid?

Explanation of the use of a circle to represent the bonding of benzene

Examples of aromatic compounds used in the following areas: dyestuffs, detergents, herbicides, pharmaceuticals

Evidence for the mechanism of ionic addition?

Formation of polyethene and polypropene

Evidence for the halogenation of alkanes?

What is a known source of free radicals?

Use of high performance liquid/IR/UV chromatography?

What is the self ionisation of water?

Causes of temporary and permanent hardness in water?

How to remove lead from water?

What does EDTA stand for?



If you know all that, you should be fine. I don't anyway.

Acciaccatura

Doing this off the top of my head with minimal study, this'll be interesting:


*Distinction between chemical reaction and nuclear reaction? In a chemical reaction, no new elements are made and it involves the gaining/losing/sharing of electrons. In nuclear reactions, new elements are formed due the the number of protons in the nucleus being affected.

*Oxidation number of oxygen in H202: +2

*What is a primary alcohol? An alcohol that has one carbon attached to the carbon with the OH

*Use of propanone and propanoic acid? Propanone-nail varnish remover/solvent
Propanoic acid - dunno

*Explanation of the use of a circle to represent the bonding of benzene - The 4th electron in carbon's covalent bond constantly change which carbon they're bonding with

*Use of high performance liquid/IR/UV chromatography? HPLC-To determine the concentration of caffeine/vitamins in drinks

*Causes of temporary and permanent hardness in water? Mg+ or Ca+ ions present

*What does EDTA stand for? Ethylene Diamene Tetraacetic acid

Yay. Eight out of God knows how many. Can't wait for that A :pac:

little sis...

Acciaccatura wrote: »

Doing this off the top of my head with minimal study, this'll be interesting:


*Distinction between chemical reaction and nuclear reaction? In a chemical reaction, no new elements are made and it involves the gaining/losing/sharing of electrons. In nuclear reactions, new elements are formed due the the number of protons in the nucleus being affected.

*Oxidation number of oxygen in H202: +2

*What is a primary alcohol? An alcohol that has one carbon attached to the carbon with the OH

*Use of propanone and propanoic acid? Propanone-nail varnish remover/solvent
Propanoic acid - dunno

*Explanation of the use of a circle to represent the bonding of benzene - The 4th electron in carbon's covalent bond constantly change which carbon they're bonding with

*Use of high performance liquid/IR/UV chromatography? HPLC-To determine the concentration of caffeine/vitamins in drinks

*Causes of temporary and permanent hardness in water? Mg+ or Ca+ ions present

*What does EDTA stand for? Ethylene Diamene Tetraacetic acid

Yay. Eight out of God knows how many. Can't wait for that A :pac:

Just having a glance, but I believe the oxidation number of oxygen is -1 in H2O2.

A use for propanoic acid is a (food) preservative I believe :rolleyes:

xJEx

Does anyone know how many equations we actually need to know?? Like there seems to be a never ending amount but what ones could we actually be asked to write a balanced equation for?

Hamza Malik

xJEx wrote: »

Does anyone know how many equations we actually need to know?? Like there seems to be a never ending amount but what ones could we actually be asked to write a balanced equation for?

There's a lot. But there's questions for heat of formation/combustion where you have to make up the equation. And then there's a couple equations for the water chapter you should know too..

And ofc there's the oxidation numbers equations you need to know how to balance

Acciaccatura

little sis... wrote: »

Just having a glance, but I believe the oxidation number of oxygen is -1 in H2O2.

A use for propanoic acid is a food preservative I believe :rolleyes:

Thank you I meant to type minus for that, sorry, but would it not be minus 2 because oxygen is a diatomic molecule? Or do they mean per atom?

xJEx

Acciaccatura wrote: »

Thank you I meant to type minus for that, sorry, but would it not be minus 2 because oxygen is a diatomic molecule? Or do they mean per atom?

They always mean per atom

little sis...

Acciaccatura wrote: »

Thank you I meant to type minus for that, sorry, but would it not be minus 2 because oxygen is a diatomic molecule? Or do they mean per atom?

I took it as an atom?
I looked it up just now to make sure and the interwebs agree with me :P


No problem just wanted to make sure that the answers you were 'sure' about were correct

Acciaccatura

xJEx wrote: »

They always mean per atom

I always get caught out with finicky things like that, thanks!

0mega

xJEx wrote: »

Does anyone know how many equations we actually need to know?? Like there seems to be a never ending amount but what ones could we actually be asked to write a balanced equation for?

The main one asked is this from the water chapter:

H20 + C02 = C02(aq)

C02(aq) + H20 = H2CO3

H2CO3 + CaCO3 = Ca(HCO3)2

xJEx

0mega wrote: »

The main one asked is this from the water chapter:

H20 + C02 = C02(aq)

C02(aq) + H20 = H2CO3

H2CO3 + CaCO3 = Ca(HCO3)2

Thanks, there seems to be so many on the course but they're not actually asked that often in the papers

CookieMonster.x

0mega wrote: »

Just looking through the syllabus, I'll pull out the hard qs:

Distinction between chemical reaction and nuclear reaction?

Example of a displacement reaction in the electrochemical series?

What is a transition element and give examples?

Uses of helium and argon related to their chemical unreactivity?

Physical properties of ionic/covalent substances?

Relationship between symmetry and polarity in a molecule?

Oxidation number of oxygen in H202

Reasons why real gases deviate from ideal gas behaviour?

Composition of LPG?

What does MTBE stand for?

What is the surface adsorption theory?

What is a primary alcohol?

Use of propanone and propanoic acid?

Explanation of the use of a circle to represent the bonding of benzene

Examples of aromatic compounds used in the following areas: dyestuffs, detergents, herbicides, pharmaceuticals

Evidence for the mechanism of ionic addition?

Formation of polyethene and polypropene

Evidence for the halogenation of alkanes?

What is a known source of free radicals?

Use of high performance liquid/IR/UV chromatography?

What is the self ionisation of water?

Causes of temporary and permanent hardness in water?

How to remove lead from water?

What does EDTA stand for?



If you know all that, you should be fine. I don't anyway.

I'm going to try these without looking these up, hopefully I'll get through them ok!
1. A chemical reaction is one in which no new element is formed as there is no change in the nucleus. A nuclear reaction involves a new element being formed with the emission of radiation (?)
2. Magnesium and copper - the magnesium ribbon turns black an the water becomes less blue (or something like it).
3. One that has an incomplete d sun level. They have variable valencies and coloured compounds. Eg. Copper.
4. Helium - used in gas chromatography but don't think that's what they're looking for.
5. Ionic are crystalline solids, made of crystal lattice. Covalent are liquids?
6. A molecule is polar if the lines of symmetry do not lie on the molecule like in water.
7. -1 I think
8. Collisions are perfectly elastic, there are forced of attraction, the space occupied by particles is not negligible in comparison to the container.
9. Butane and propane.
10. Methyl tert butyl ether.
11. Gases adsorb onto solids eg. Catalytic converters in cars. The products are formed and then leave the solid.
12. One in which the -oh group is attached to one other carbon (I think).
13. Propanone - organic solvent eg nail polish remover. Propanoic acid - food preservative I think.
14. The electrons in benzene are not localised. Also the carbon to carbon bonds are of equal length.
15. Dyes naphthalene (something along the lines of that I think)
Pharmaceuticals: aspirin. Can't remember the others.
16. Carbonium ion
17. Add many molecules of Ethene together to create a polymer. Same for propene.
18. Not sure but halogenated Allan's are flame retardants so could be that they are not flammable - used in fire extinguishers etc.
19. UV light from the sun.
20. HPLC: Used to analyse foods - vitamins.
IR - analyse heavy metals - fingerprint
UV - analyse compounds
21. Water breaks up into h+ and oh-??
22. Calcium and magnesium ions. Temp: sulfates and perm: carbonates I think
23. Precipitation: add 2cl- to form insoluble pbcl2.
24. Ethylene diamine tetra acetic acid.

Hope some of those are right :P I need a bit more detail in a few but it's good seeing as I haven't looked at chemistry in weeks!

weirdspider

0mega wrote: »

Just looking through the syllabus, I'll pull out the hard qs:

Distinction between chemical reaction and nuclear reaction? Chemical reaction involves the making and breaking of bonds and the formation of products. In nuclear reactions changes only occur in the nucleus. Transmutation in nuclear reactions, not in chemical rxns.

Example of a displacement reaction in the electrochemical series? Hmm would this be electroplating any metal onto an object?

What is a transition element and give examples? One that forms one ion with a partially filled d sublevel. Manganese

Uses of helium and argon related to their chemical unreactivity? Helium in balloons and argon for insulation in houses

Physical properties of ionic/covalent substances? Ionic-Composed of ions/a crystal lattice, solids at room temp./conduct electricity when molten or dissolved in water/hard and brittle, higher b.p. Covalent-consists of individual molecules/liquids, gases or soft solids a room temp./lower b.p/don't conduct electricity

Relationship between symmetry and polarity in a molecule? If the molecule is symmetrical the centre of positive charge coincides with the centre of negative charge giving a non polar molecule even if the bonds are polar

Oxidation number of oxygen in H202 -1 each

Reasons why real gases deviate from ideal gas behaviour? Attractive forces exist between gaseous molecules. Under conditions of high pressure and low temp molecules are close together so the distances between them are no longer negligible compared to the volume they occupy

Composition of LPG? Liquid petroleum gases, gases which are easily liquified under pressure

What does MTBE stand for? Methyl Tertiary Butyl Ether

What is the surface adsorption theory? Molecules adsorb onto surface are held onto by temporary bonds, increased concentration means incr. probability of rxn, molecules on surface react, desorption occurs when the products leave the surface

What is a primary alcohol? One that has one carbon atom attached to the OH group

Use of propanone and propanoic acid? Propanone-nail polish remover, propanoic acid-for preserving food

Explanation of the use of a circle to represent the bonding of benzene-bonds are constantly alternating between double and single

Examples of aromatic compounds used in the following areas: dyestuffs, detergents, herbicides, pharmaceuticals-Penicillin is the only one I know here? Would you mind giving an answer?

Evidence for the mechanism of ionic addition? Negative ions indicate the presence of a positive intermediate, products such as 1, 2 dibromoethane, 2 bromoethanol and 1bromo 2 chloroethane are formed when bromine water is mixed with ethene in the presence of sodium chloride

Formation of polyethene and polypropene: H-H-C=C-H-H and
CH3-H-C=C-H-CH3 and remove the double bonds when drawing repeating units

Evidence for the halogenation of alkanes? Reaction only proceeds in the presence of UV light, radical promoters speed up the rate of reaction and products such as 1, 2dicholormethane, Cl2 and ethane are formed

What is a known source of free radicals? Umm are they in carcinogens like cigarette smoke?

Use of high performance liquid/IR/UV chromatography? HPLC-identify ions in orange juice IR-Forensics UV-To identify the presence of particular ions

What is the self ionisation of water? H2O<--->H^+ +OH^-

Causes of temporary and permanent hardness in water? Temp: Calcium hydrogencarbonate, magnesium hydrogencarbonate Perm: Calcium sulphate, Magnesium sulphate, Calcium chloride, Mg chloride

How to remove lead from water? Precipitation reactions

What does EDTA stand for? Ethylene diamine tetra acetic acid



If you know all that, you should be fine. I don't anyway.

-

weirdspider

0mega wrote: »

Just looking through the syllabus, I'll pull out the hard qs:

Distinction between chemical reaction and nuclear reaction?

Example of a displacement reaction in the electrochemical series?

What is a transition element and give examples?

Uses of helium and argon related to their chemical unreactivity?

Physical properties of ionic/covalent substances?

Relationship between symmetry and polarity in a molecule?

Oxidation number of oxygen in H202

Reasons why real gases deviate from ideal gas behaviour?

Composition of LPG?

What does MTBE stand for?

What is the surface adsorption theory?

What is a primary alcohol?

Use of propanone and propanoic acid?

Explanation of the use of a circle to represent the bonding of benzene

Examples of aromatic compounds used in the following areas: dyestuffs, detergents, herbicides, pharmaceuticals

Evidence for the mechanism of ionic addition?

Formation of polyethene and polypropene

Evidence for the halogenation of alkanes?

What is a known source of free radicals?

Use of high performance liquid/IR/UV chromatography?

What is the self ionisation of water?

Causes of temporary and permanent hardness in water?

How to remove lead from water?

What does EDTA stand for?



If you know all that, you should be fine. I don't anyway.

Cool this can be the new quiz!