Qxi.xli
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In the MS to that questions it says dont allow the ions hit the CHARGED plate, why is that? cuz i thought the plat is negative??


Also, in a different question, it says that the charged ions are accelerated by an electric field? but i thought they were accelerated by a negatively charged plate??

Thank you xxx
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Hellllpppp
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I would assume it says don’t allow charged because it’s not specific enough. It’s best to say negatively charged plate.

The ions in mass spectrometry are accelerated by an electric field so they all have the same kinetic energy during ion drift stage before they reach the detector.

I hope this helps
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Pigster
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(Original post by vix.xvi)
In the MS to that questions it says dont allow the ions hit the CHARGED plate, why is that? cuz i thought the plat is negative??


Also, in a different question, it says that the charged ions are accelerated by an electric field? but i thought they were accelerated by a negatively charged plate??

Thank you xxx
The positive ions are attracted to the negative plate. It is an electric field that causes the force.

If the positive ions hit the plate, they gain an e- and are no longer charged, so would not be deflected by the magnetic field.
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Qxi.xli
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(Original post by Hellllpppp)
I would assume it says don’t allow charged because it’s not specific enough. It’s best to say negatively charged plate.

The ions in mass spectrometry are accelerated by an electric field so they all have the same kinetic energy during ion drift stage before they reach the detector.

I hope this helps
Thank you But the MS said just 'plate' and below that said don't allow charged plate
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EierVonSatan
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(Original post by vix.xvi)
Thank you But the MS said just 'plate' and below that said don't allow charged plate
The markscheme says do not allow (transfer of electrons) FROM the charged plate
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Qxi.xli
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(Original post by EierVonSatan)
The markscheme says do not allow (transfer of electrons) FROM the charged plate
This is the MS xx

Electron(s) transferred / flow (at the detector)
M1 must refer to electron flow at the detector.
If M1 incorrect CE = 0/2
1
(From detector / plate) to the (+) ion
Do not allow from a charged plate
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Qxi.xli
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(Original post by EierVonSatan)
The markscheme says do not allow (transfer of electrons) FROM the charged plate
wait also I thought the electrons are transferred from the plate to the ions tho, cuz they are positively charged?
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EierVonSatan
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(Original post by vix.xvi)
wait also I thought the electrons are transferred from the plate to the ions tho, cuz they are positively charged?
I think you're confusing the plate that causes acceleration of the ions (negatively charged) with the detector (not charged)?
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Hellllpppp
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(Original post by vix.xvi)
wait also I thought the electrons are transferred from the plate to the ions tho, cuz they are positively charged?
Here a quote from the AQA worksheet on mass spec I think might help

“The positive ions hit a negatively charged electric plate. When they hit the detector plate, the positive ions are discharged by gaining electrons from the plate. This generates a movement of electrons and hence an electric current that is measured. The size of the current gives a measure of the number of ions hitting the plate”
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EierVonSatan
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(Original post by Hellllpppp)
Here a quote from the AQA worksheet on mass spec I think might help

“The positive ions hit a negatively charged electric plate. When they hit the detector plate, the positive ions are discharged by gaining electrons from the plate. This generates a movement of electrons and hence an electric current that is measured. The size of the current gives a measure of the number of ions hitting the plate”
That's from the student guidance sheet, isn't it?

It's a confused statement sadly, if you look up at the ionisation diagrams they clearly show the negative plate is used to accelerate ions following ionisation (to a constant kinetic energy using something called a reflectron). If the detector was also accelerating ions after this it would mess up the TOF.

https://www.agilent.com/cs/library/t...1-Dec-2003.pdf
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Qxi.xli
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(Original post by EierVonSatan)
I think you're confusing the plate that causes acceleration of the ions (negatively charged) with the detector (not charged)?
ahh I see thank you! But in the quote below, doesn't it suggest that the detector plate and the electric plate are the same? xx sorry to keep disturbing you.
(Original post by Hellllpppp)
Here a quote from the AQA worksheet on mass spec I think might help

“The positive ions hit a negatively charged electric plate. When they hit the detector plate, the positive ions are discharged by gaining electrons from the plate. This generates a movement of electrons and hence an electric current that is measured. The size of the current gives a measure of the number of ions hitting the plate”
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Hellllpppp
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The worksheet separates the different stages - the quote I gave is from the detection stage. So the electric plate is the detector.

Before the quote it talks about the acceleration and it just says the electrons are accelerated by an electric field - this electric field is created by a different electric plate - look at the diagrams.

https://filestore.aqa.org.uk/resourc...5-SG-TOFMS.PDF
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EierVonSatan
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(Original post by vix.xvi)
ahh I see thank you! But in the quote below, doesn't it suggest that the detector plate and the electric plate are the same? xx sorry to keep disturbing you.
(Original post by Hellllpppp)
The worksheet separates the different stages - the quote I gave is from the detection stage. So the electric plate is the detector.

Before the quote it talks about the acceleration and it just says the electrons are accelerated by an electric field - this electric field is created by a different electric plate - look at the diagrams.

https://filestore.aqa.org.uk/resourc...5-SG-TOFMS.PDF
It does suggest that, but I'm convinced it is incorrect.

I can't find another description that agrees with what that sheet says - not in the textbook, revision guide or more widely online. Have a look at AQA's detailed teaching notes on detection: https://filestore.aqa.org.uk/resourc...ECTROMETRY.PDF
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