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

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!

0mega

Source of free radicals - tetraethyllead

I'll look up the answers to some other ones later. I don't know myself.

outnumbered

Diverting from the quiz, If one is asked to determine if a reaction is redox, How do you do it?
I assigned oxidation numbers, now what?

0mega

outnumbered wrote: »

Diverting from the quiz, If one is asked to determine if a reaction is redox, How do you do it?
I assigned oxidation numbers, now what?

See if there's a change in the oxidation numbers from the left side to the right, or vice versa.

For example, in the oxidation of ethanol to ethanal.

Chromium is reduced from +6 to +3 from the left side to the right.

Therefore electrons have been gained/lost. It's a redox reaction.

outnumbered

0mega wrote: »

See if there's a change in the oxidation numbers from the left side to the right, or vice versa.

For example, in the oxidation of ethanol to ethanal.

Chromium is reduced from +6 to +3 from the left side to the right.

Therefore electrons have been gained/lost. It's a redox reaction.

Thank You!!!
So basically you identified what has been oxidised and what has been reduced. If something has been oxidised/reduced it implies redox????

meleanor

Regarding the quiz: I think for metal displacement they'd be looking for the magnesium/zinc in copper sulfate demonstrations?

xJEx

outnumbered wrote: »

Thank You!!!
So basically you identified what has been oxidised and what has been reduced. If something has been oxidised/reduced it implies redox????

Yep that's all you gotta do. Any change in any of the numbers = redox

outnumbered

xJEx wrote: »

Yep that's all you gotta do. Any change in any of the numbers = redox

Gracias!

RabbitHearted

Can someone state Pauli's Exclusion Principle for me? It's not in my book and we never mentioned it?
Also, earlier in the thread a couple of you mentioned not being able to do the ethanoic acid/ethanal exp.s.. you should come to our class we did all of them, including ones that have been completly taken off the course ie ones that were on the old course and the prep room is full of banned chemicals because apparently there only accumatively carcinogenic so were grand
Also the ethanal exp was brilliant, we set the floor on fire with the most amazing green blue flames. Safety first..

outnumbered

When there is a system in equilibrium and it asks what change of Kc would an increase in pressure have:
I know you count no of moles on boths sides la la la .
But what change of Kc occurs. Say the reactant on the right increase in concentration, what effect does this have on Kc. For an example refer to 201o q7 e

xJEx

outnumbered wrote: »

When there is a system in equilibrium and it asks what change of Kc would an increase in pressure have:
I know you count no of moles on boths sides la la la .
But what change of Kc occurs. Say the reactant on the right increase in concentration, what effect does this have on Kc. For an example refer to 201o q7 e

Always get stuck on this one! Pretty sure it's no change - Kc is temp. dependent, not affected by changes in concentration or pressure