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Chemistry C1,C2,C3 - May 2014

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Original post by majmuh24
Bombarded with electrons to ionize, vaporized and accelerated through tube at different speeds depending on mass (F=dρdtF = \dfrac{d \rho}{d t} ), deflected by magnetic field depending on speeds and charges, mass spectrometer detects these and uses them to find out the mass of the elements and the relative composition.

Molecular ion peak corresponds to RMM of molecule with one electron removed.

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Ah okay :tongue: thank you :h:

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Original post by thechemistress
Determined to not **** up this exam after Biology's failure xD So yeah, hopefully it will go well. If anybody has some challenging C2 and C3 questions, please fire them at me now, thanks :biggrin:


Why is citric acid weaker than sulfuric acid?

Explain the reactions involved in the extraction of aluminum.

How would you work out the energy released when one mole of methanol is combusted?


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(edited 9 years ago)
,.
Bumped for anyone that's doing Chem tomorrow :tongue:

Anyway, could someone answer my question - Why is it better to put the reactant of known concentration in the burette in a titration? My teacher said that it's preferred without much of an explanation, but I thought you could do it either way since when you sub all your known values in, it just reduces down into a normal linear equation whichever way you do it :s-smilie:

I was thinking it was just a matter of convenience because of the indicator range of phenolphthalein and that the alkali is normally added to the acid

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(edited 9 years ago)
Original post by majmuh24
Is it a fair test?
Is there only one variable being changed?
How could uncertainty be introduced into the experiment?
Is there potential for random or experimental error?
Are the conclusions valid?
Is it reliable and reproducible?

You just have to go through all of these things and see if there's one that it doesn't fit in with.

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What is uncertainty?
Original post by Winading001
What is uncertainty?


http://en.wikipedia.org/wiki/Measurement_uncertainty

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Original post by majmuh24
Why is citric acid weaker than sulfuric acid?

Explain the reactions involved in the extraction of aluminum.

How would you work out the energy released when one mole of methanol is combusted?


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Sorry, just seen these xD Will do them once I get home, phone signal is crap xD
Original post by majmuh24
Bumped for anyone that's doing Chem tomorrow :tongue:

Anyway, could someone answer my question - Why is it better to put the reactant of known concentration in the burette in a titration? My teacher said that it's preferred without much of an explanation, but I thought you could do it either way since when you sub all your known values in, it just reduces down into a normal linear equation whichever way you do it :s-smilie:

I was thinking it was just a matter of convenience because of the indicator range of phenolphthalein and that the alkali is normally added to the acid

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I think its because if you put the known concentration in the conical flask and it neutralised with the unknown from the you wont know how much of the known solution neutralised the unknown solution so there would be too many unknowns. I suppose you could work it out but there not much point
I'm screwed..literally forgot 2a and 2b.. Need. To revise all of it tonight. Is that possible ? :/
Original post by MissVenus
I think its because if you put the known concentration in the conical flask and it neutralised with the unknown from the you wont know how much of the known solution neutralised the unknown solution so there would be too many unknowns. I suppose you could work it out but there not much point


Yes you would, there would be a known volume and concentration of the substance in the conical flask :s-smilie:

That's why I'm confused about it, it seems like the same method to me :confused:

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Original post by majmuh24
Yes you would, there would be a known volume and concentration of the substance in the conical flask :s-smilie:

That's why I'm confused about it, it seems like the same method to me :confused:

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Honestly, just listen to your teacher, the examiners mark a hell of a lot of papers and if its worded in a way there not familiar with theyll just mark it wrong, thats why your teacher says to write a known volume, to ensure that the markers give u full marks, also dont forget about white tile and spinning flask whilst adding acid but i doubt titration will be in, its been two years in a row
@beefman10 dude yeah that is possible, trust me, just look over it quicktime, I don't barely revise at all cause im lazy asf and so but you can do it lol, I have to revise 2a and 2b aswell as 3a and 3b and I hate it:frown:
(edited 9 years ago)
Reply 32
Avatar for TMudd
TMudd
1
Hey guys for those revising for C3 just thought I would share my mnemonic for the Flame test colours. Not sure if it will work for any of you guys but it seemed to work for me I can now remember them all :smile:

Crying - Crimson
Your - Yellow
Little - Lilac
Brain - Brick Red
Goodnight - Green


Like a - Lithium
Stupid - Sodium
Person who - Potassium
Can't - Calcium
Breath - Barium
I've just gone over the whole C2 specification, using a CGP Additional Science revision guide. There is, however, something I don't understand;

Making insoluble salts- precipitation reactions

The Revision guide states that 'you just need to pick two solutions that contain the ions you need'.

How do you know which solutions you can pick for the specific reaction?
Also, is this all we need to know on this topic (and the fact you have to then filter the salt out etc.)?

Oh and also, do you have to know exactly how Magnesium, Aluminium, Zinc, Iron and Copper react with Dilute HCl? Or do you simply have to know that 'the more reactive the metal, the faster the reaction'?
Original post by TMudd
Hey guys for those revising for C3 just thought I would share my mnemonic for the Flame test colours. Not sure if it will work for any of you guys but it seemed to work for me I can now remember them all :smile:

Crying - Crimson
Your - Yellow
Little - Lilac
Brain - Brick Red
Goodnight - Green


Like a - Lithium
Stupid - Sodium
Person who - Potassium
Can't - Calcium
Breath - Barium


That's awesome!!!
Btw do we need to know how a calorimetry is taken? If so that could be the six marker
Reply 35
Avatar for TMudd
TMudd
1
Original post by Joshua697
That's awesome!!!
Btw do we need to know how a calorimetry is taken? If so that could be the six marker


As far as I know yes we do I hope that's a six marker although I doubt it. If it comes up would probably be a 2 mark equation question, There was 2 six markers in Biology so I would assume 2 Six markers in the Chemistry Possible one on Titration..
Original post by passwordisrevise
@beefman10 dude yeah that is possible, trust me, just look over it quicktime, I don't barely revise at all cause im lazy asf and so but you can do it lol, I have to revise 2a and 2b aswell as 3a and 3b and I hate it:frown:


Good, I'll try to do my best. Learnt 2a. Now 2b
Any key words which I should memorizes for c2??
Original post by Beefman10
Any key words which I should memorizes for c2??

I'd definitely know the definitions and try to incorporate as many of them in your answers as possible, words such as:

•

Inter-molecular/electrostatic forces

•

Yield

•

Noble gas configuration

•

Giant Lattice

•

Covalent, Ionic and Metallic bonding

•

Exothermic, Endothermic

•

Neutralisation

•

Oxidation, Reduction

•

Thermal Decomposition

•

Delocalised electrons, Sea of electrons

•

Fullerenes (Buckminister and Nanotubes)

•

Malluable

•

Monomer

•

Conductor

•

Polymer

•

Shape memory alloys (Nitinal)

•

Low density/high density polyethene

•

Thermosoftening, Thermosetting

•

Catalyst

•

Activation energy

•

Surface area:volume ratio

•

Precipitation

•

Collision theory

•

Acids, bases and salts

•

Effluent

•

Electrolyte

•

Anode and cathode

•

Cryolyte

Original post by S.Ahmad
I'd definitely know the definitions and try to incorporate as many of them in your answers as possible, words such as:

•

Inter-molecular/electrostatic forces

•

Yield

•

Noble gas configuration

•

Giant Lattice

•

Covalent, Ionic and Metallic bonding

•

Exothermic, Endothermic

•

Neutralisation

•

Oxidation, Reduction

•

Thermal Decomposition

•

Delocalised electrons, Sea of electrons

•

Fullerenes (Buckminister and Nanotubes)

•

Malluable

•

Monomer

•

Conductor

•

Polymer

•

Shape memory alloys (Nitinal)

•

Low density/high density polyethene

•

Thermosoftening, Thermosetting

•

Catalyst

•

Activation energy

•

Surface area:volume ratio

•

Precipitation

•

Collision theory

•

Acids, bases and salts

•

Effluent

•

Electrolyte

•

Anode and cathode

•

Cryolyte


I know most of these, just the odd ones whitch I need to learn. Thank you

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