[dtin]

(Original post by letsbehonest)
I hope we get a straight forward questions. Some calculations and also a description of titration, water cycle, periodic table stuff.

What is 1bii)? evapouration? and what else?

and also the last calculation 5bii) ?
Is 5bi) just asking for a mean? Lol the question is so weird.

the first question on very back page is asking for a mean but the 2nd one is harder look in the mark scheme for that one

[tiny278]

(Original post by _soph1)
I think we need to know like mass spectrometry, infra red spectrometry and atomic absorption spectroscopy but i don't know in how much detail? Does anyone know of any others we need to learn?

My teacher said it isn't one of the most important thins to revise so i'm not going to worry about it too much

you only need to know a bit about each, but not how each works

[tiny278]

FLAME TEST RESULTS:
I know its really stupid but this helps me remember them ahaa:
Barium- bogey- green
lithium- lipstic- bright red
Calcium- castle- brick red
Sodium- Sun- yellowy orange
potassium- purple- lilac
magnesium/ammonium- no colour..

hope it helps :P

[Ashley is a baws]

Ahhh this exam is tomorrow :L i don't get moles or reversible reactions XD Hopefully il just manage with everything else though

[SophieLisa96]

chemistry aqa unit 2 january 2012 past paper???

[nacho1996]

Do you get a copy of the periodic table and reactivity series with the unit 2 exam?


This was posted from The Student Room's iPhone/iPad Ap

[0000000000]

Hey guys,

I'm revising for C2 tomorrow, can you let me know all of the equations that I may need to learn?

[usycool1]

(Original post by nacho1996)
Do you get a copy of the periodic table and reactivity series with the unit 2 exam?


This was posted from The Student Room's iPhone/iPad Ap

Yup

[rainerised]

Why does increasing pressure or concentration increase the rate of reaction? And whats the difference between pressure and concentration?

[steviep14]

(Original post by rainerised)
Why does increasing pressure or concentration increase the rate of reaction? And whats the difference between pressure and concentration?

Basically if you increase pressure, more atoms are in a smaller volume meaning there will be more collisions more frequently decreasing the time taken to reach the activation energy.

Pressure = Gas State
Concentration = Liquid/Solution State

There isn't much difference just the words used for the medium involved

[steviep14]

(Original post by 0000000000)
Hey guys,

I'm revising for C2 tomorrow, can you let me know all of the equations that I may need to learn?

Well you definitely will need:

Mass = Mol x Ram
% Yield = (Products Obtained) / (Max Products Obtainable)
Atom Economy = RFM of Useful Products / RFM of all product
Rate = Amount of Product Formed / Time
% of a Substance in a Compound = (RFM of Substance / RFM of Compound) x 100
Half Equations - Pb²⁺ + 2e^- --> Pb
(For the Half Equations you are making a net charge ion have 0 charge)

I think that is all for C2

[rainerised]

(Original post by steviep14)
Basically if you increase pressure, more atoms are in a smaller volume meaning there will be more collisions more frequently decreasing the time taken to reach the activation energy.

Pressure = Gas State
Concentration = Liquid/Solution State

There isn't much difference just the words used for the medium involved

Thanks

[steviep14]

(Original post by Ashley is a baws)
Ahhh this exam is tomorrow :L i don't get moles or reversible reactions XD Hopefully il just manage with everything else though

Reversible Reactions:

In a closed System:

No products can escape or get in to affect the reaction meaning eventually a forward reaction will equal a backwards reaction in dynamic equilibrium - Changing Temperature will cause a change:
Exothermic: Temp Increase = Decreased Yield / Temp Decrease = Increased Yield - So increasing the temperature favours the backward reaction
Endothermic: Temp Increase = Increased Yield / Temp Decrease = Decreased Yield - So decreasing the temperature favours the forward reaction.

In an open system:

Products CAN escape or get in meaning the forward reaction continues to completion.

In terms of Moles:

Mass = Mol x Ram
or Mol = Mass/Ram - With Moles you need to look at the equation..
if you work out the moles of a substance with "1 Mole" (Look at the number preceding the Substance) and the other substance has "1 Mole" you need to do nothing:

1 Mole = 1CO₂ OR CO₂
2 Moles = 2CO₂
3 Moles = 3CO₂ etc.

Now if you have a worked out a substance with 1 mole and the other substance is 3 moles..
Mol Ratio = 1:3
So when working with the other substance you times the moles by three?
Mol Ratio = 1:2 (Times by 2)

If you work out a substance with 3 Moles (3CO₂)
and the other substance is 1 mole
Mol Ratio = 3:1 (Divide by 3)

Hope I helped

[steviep14]

(Original post by rainerised)
Thanks

No worries Just remember that if you change Temperature/Pressure mention collisions/energy/volume

For Temp: More Kinetic Energy, particles move with more speed, collisions with more force, lower activation energy

For Pressure: More atoms in Less Space, More frequent Collisions, Lower activation energy

and this should always get you full marks

[tssf_skye]

This is my first post on this, so hi :-)

For anyone struggling on the haber process and stuff, i find that the hardest part aswell the only things you really need to know is that:

The best yield is at low temperatures because the forward reaction is exothermic. (So increase in temp = low yield decrease in temp = high yield)

If the temperature was any lower the rate of reaction would be too slow, and for they use 200atm because there are less product molecules than reactant molecules
Unless, they ask you a question like:
'Why does changing the pressure at equilibrium not affect the yield'

it's because the number of reactant and product molecules are equal on both sides of the equation

I dunno if that's helped? haha :-)

[LiamJD]

Okay, this probably the wrong place for this, but it's kind of desperate times for me now.

Element: A214H: Science A: Unit 4 (Ideas) Hgh
Component: A214/02: Science A: Unit 4 (Ideas) Hgh

This is the paper that I'm doing on the 24/05/12 (tommorrow). I just need to know what I'm doing, like the 3 topics. Thanks.

[Tweak6]

Does anybody have the mark scheme for the Chem unit 3 Jan 2012 paper??? My teacher gave use the paper and no mark scheme :/

[tinkerbell1109]

(Original post by nacho1996)
Do you get a copy of the periodic table and reactivity series with the unit 2 exam?


This was posted from The Student Room's iPhone/iPad Ap

Yes you do

[tinkerbell1109]

(Original post by tssf_skye)
This is my first post on this, so hi :-)

For anyone struggling on the haber process and stuff, i find that the hardest part aswell the only things you really need to know is that:

The best yield is at low temperatures because the forward reaction is exothermic. (So increase in temp = low yield decrease in temp = high yield)

If the temperature was any lower the rate of reaction would be too slow, and for they use 200atm because there are less product molecules than reactant molecules
Unless, they ask you a question like:
'Why does changing the pressure at equilibrium not affect the yield'

it's because the number of reactant and product molecules are equal on both sides of the equation

I dunno if that's helped? haha :-)

Thanks! =) and good luck for tomorrow

[piratefinn]

(Original post by Tweak6)
Does anybody have the mark scheme for the Chem unit 3 Jan 2012 paper??? My teacher gave use the paper and no mark scheme :/

WHich exam board? If it's AQA they have on the website that stuff published.