AS Chemistry- helping each other out!
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Does anyone know a site with loads of AQA amount of substance practice questions?
As anyone found the June 2014 papers for F321 & F322?
http://gyazo.com/3a9590bb801c8a389579b255f2e490d1
For part b why is it D not A? Surely as the moles are equal pressure makes no difference?
For part b why is it D not A? Surely as the moles are equal pressure makes no difference?
Original post by BBeyond
http://gyazo.com/3a9590bb801c8a389579b255f2e490d1
For part b why is it D not A? Surely as the moles are equal pressure makes no difference?
For part b why is it D not A? Surely as the moles are equal pressure makes no difference?
I think its nothing to do with the position of equilibrium. If you compress the gas the I2 molecules are closer together so the purple colour would be stronger (in a similar way to how orange squash is more orange the more conc it is)
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Original post by samb1234
I think its nothing to do with the position of equilibrium. If you compress the gas the I2 molecules are closer together so the purple colour would be stronger (in a similar way to how orange squash is more orange the more conc it is)
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ah G shout, cheers
Original post by BeckyWarkup
On the outline it said amount of substance and group 2, we have the paper tomorrow and apparently it has identifying group 2 compounds from how they react
apparently they tell you in the question that mg(oh)2 , ca(oh)2, sr(oh)2, ba(oh)2; same thing mg, ca, sr and ba with SO4
u need to know how each of these react and how to identify them.
they are all colourless and in solution.
this is not information from the paper, just what our teacher told us
Hai
I don't get this:
"Graphite can conduct electricity well betweenlayers because one electron per carbon is free anddelocalised, so electrons can move easily alonglayers.
It does not conduct electricity between layersbecause the energy gap between layers is toolarge for easy electron transfer."
Says it does.. but then it says it doesn't...
I don't get this:
"Graphite can conduct electricity well betweenlayers because one electron per carbon is free anddelocalised, so electrons can move easily alonglayers.
It does not conduct electricity between layersbecause the energy gap between layers is toolarge for easy electron transfer."
Says it does.. but then it says it doesn't...
Original post by Dee .. ♥
Hai
I don't get this:
"Graphite can conduct electricity well betweenlayers because one electron per carbon is free anddelocalised, so electrons can move easily alonglayers.
It does not conduct electricity between layersbecause the energy gap between layers is toolarge for easy electron transfer."
Says it does.. but then it says it doesn't...
I don't get this:
"Graphite can conduct electricity well betweenlayers because one electron per carbon is free anddelocalised, so electrons can move easily alonglayers.
It does not conduct electricity between layersbecause the energy gap between layers is toolarge for easy electron transfer."
Says it does.. but then it says it doesn't...
It means it conducts within a sheet but not between them. Graphite is formed of hundreds of layers. Within each layer there is one delocalised electron per carbon which means that the layer conducts electricity extremely well. However there is a small gap between that layer and the layer below so it cannot conduct in that direction
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Original post by BBeyond
ah G shout, cheers
Isnt it just that there are equal amount of moles on each side so there will be no visible change ?
Original post by shhh123
Isnt it just that there are equal amount of moles on each side so there will be no visible change ?
No. It is nothing to do with equilibrium as far as I'm aware
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Original post by samb1234
Im sure it does cus of you first have look at the number of moles on each side then see if eqilibria will shift to side with a side of fewer moles in this case there is two moles on the LHS and RHS so there will be no overall effect
Original post by shhh123
Isnt it just that there are equal amount of moles on each side so there will be no visible change ?
Yes exactly there are equal amount of moles on each side so there will be no effect on equilibrium.
Therefore when compressed the colour will be darker as the coloured particles are closer together.
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Original post by shhh123
Im sure it does cus of you first have look at the number of moles on each side then see if eqilibria will shift to side with a side of fewer moles in this case there is two moles on the LHS and RHS so there will be no overall effect
Correct equilibrium will not move. However reducing the volume has the effect of 'concentrating' the colour as you still have the same number of coloured I2 molecules but in a smaller space, therefore they are closer and the colour appears stronger
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Anyone have any notes for either F331 or F332 that follows all the points on the spec?
Also how are you guys revising?
Has anyone done the evaluative practical task for OCR A about ketones? if so can you please give an idea of the things I need to know/revise as ive got mine in 2 days. thank you 
Can somebody check my answer to a titration question please?
20.45cm3 of H2SO4, 0.05moldm-3 was required to neutralise 25cm3 of NH3. What is the concentration of NH3?
Equation is H2SO4 + 2NH3 --> (NH4)2S04
Moles of H2S04 = 0.05 x 20.45 / 1000 = 1.0225x10-3 mol
1:2 ratio so moles of NH3 = 2.045x10-3 mol
Concentration = moles / volume
2.045x10-3 / 0.025 = 0.0818 moldm-3
20.45cm3 of H2SO4, 0.05moldm-3 was required to neutralise 25cm3 of NH3. What is the concentration of NH3?
Equation is H2SO4 + 2NH3 --> (NH4)2S04
Moles of H2S04 = 0.05 x 20.45 / 1000 = 1.0225x10-3 mol
1:2 ratio so moles of NH3 = 2.045x10-3 mol
Concentration = moles / volume
2.045x10-3 / 0.025 = 0.0818 moldm-3
Original post by prophetkid
Can somebody check my answer to a titration question please?
20.45cm3 of H2SO4, 0.05moldm-3 was required to neutralise 25cm3 of NH3. What is the concentration of NH3?
Equation is H2SO4 + 2NH3 --> (NH4)2S04
Moles of H2S04 = 0.05 x 20.45 / 1000 = 1.0225x10-3 mol
1:2 ratio so moles of NH3 = 2.045x10-3 mol
Concentration = moles / volume
2.045x10-3 / 0.025 = 0.0818 moldm-3
20.45cm3 of H2SO4, 0.05moldm-3 was required to neutralise 25cm3 of NH3. What is the concentration of NH3?
Equation is H2SO4 + 2NH3 --> (NH4)2S04
Moles of H2S04 = 0.05 x 20.45 / 1000 = 1.0225x10-3 mol
1:2 ratio so moles of NH3 = 2.045x10-3 mol
Concentration = moles / volume
2.045x10-3 / 0.025 = 0.0818 moldm-3
Looks right
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Right can someone help me out it is to do with analytical techniques.
1). What is meant by the molecular ion
The molecular ion is a molecule that has lost an electron in the mass spectrometer forming a positive ion with a radical.
2). What is the M peak?
The M peak is the peak that represents the molecular ion with the biggest M/Z value
3). How do fragments get formed?
Not entirely sure, possibly something to do with the bombarding of the electrons.
4). Which parts of a molecule absorb infra-red?
The covalent bonds
5). Why do most infra- red spectra of organic molecules have a strong, sharp peak at around 3000cm^-1?
Most organic molecules have a C-H bond.
6). On an infra-red spectrum, what is meant by the 'fingerprint region'
It is the region which is specific to the compound. Can someone explain this bit to me a bit more. Do we ever use it and if we do how so?
Thanks
1). What is meant by the molecular ion
The molecular ion is a molecule that has lost an electron in the mass spectrometer forming a positive ion with a radical.
2). What is the M peak?
The M peak is the peak that represents the molecular ion with the biggest M/Z value
3). How do fragments get formed?
Not entirely sure, possibly something to do with the bombarding of the electrons.
4). Which parts of a molecule absorb infra-red?
The covalent bonds
5). Why do most infra- red spectra of organic molecules have a strong, sharp peak at around 3000cm^-1?
Most organic molecules have a C-H bond.
6). On an infra-red spectrum, what is meant by the 'fingerprint region'
It is the region which is specific to the compound. Can someone explain this bit to me a bit more. Do we ever use it and if we do how so?
Thanks
Original post by Super199
Right can someone help me out it is to do with analytical techniques.
1). What is meant by the molecular ion
The molecular ion is a molecule that has lost an electron in the mass spectrometer forming a positive ion with a radical.
2). What is the M peak?
The M peak is the peak that represents the molecular ion with the biggest M/Z value
3). How do fragments get formed?
Not entirely sure, possibly something to do with the bombarding of the electrons.
4). Which parts of a molecule absorb infra-red?
The covalent bonds
5). Why do most infra- red spectra of organic molecules have a strong, sharp peak at around 3000cm^-1?
Most organic molecules have a C-H bond.
6). On an infra-red spectrum, what is meant by the 'fingerprint region'
It is the region which is specific to the compound. Can someone explain this bit to me a bit more. Do we ever use it and if we do how so?
Thanks
1). What is meant by the molecular ion
The molecular ion is a molecule that has lost an electron in the mass spectrometer forming a positive ion with a radical.
2). What is the M peak?
The M peak is the peak that represents the molecular ion with the biggest M/Z value
3). How do fragments get formed?
Not entirely sure, possibly something to do with the bombarding of the electrons.
4). Which parts of a molecule absorb infra-red?
The covalent bonds
5). Why do most infra- red spectra of organic molecules have a strong, sharp peak at around 3000cm^-1?
Most organic molecules have a C-H bond.
6). On an infra-red spectrum, what is meant by the 'fingerprint region'
It is the region which is specific to the compound. Can someone explain this bit to me a bit more. Do we ever use it and if we do how so?
Thanks
Fragments are indeed formed by the bombarding of electrons which takes place during ionisation. If the electron hits the molecule with enough energy it can potentially break the bonds forming a fragment. The fingerprint region is the region of an ir spec which is due to the stretching of the various bonds. The fingerprint region is formed of a large number of small absorptions and as far as I'm aware all you need to know is that this pattern is unique
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