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AQA CHEM5 A2 Chemistry-June 17th 2014

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Reply 80
Avatar for zuzu096
zuzu096
I feel like I'm being really stupid with this BUT why are compounds with high oxidation states eg MnO4- oxidising agents and therefore are reduced? I thought because of their negative charge they would be oxidised and lose electrons?
Original post by MySquishy!
Yeah, I do maths too so I'm not finding all the calculations too bad, although there's definitely some stuff in thermodynamics that I need some practice on!


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Sorry, didn't see this, I do agree with you there
Original post by zuzu096
I feel like I'm being really stupid with this BUT why are compounds with high oxidation states eg MnO4- oxidising agents and therefore are reduced? I thought because of their negative charge they would be oxidised and lose electrons?

Not quite sure I understand your question. Oxidation agents oxidise other things, and so get reduced themselves (electrons don't just come from thin air)
Reply 82
Avatar for Stakesby
Stakesby
Anybody doing the Empas? In AS my empa brought me wayyy down! Because I have no idea what to study for it?? Or how to... Anybody got any tips? I'm resisting last years empa and I'm doing this years ...


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Reply 83
Avatar for Suky
Suky
1
Original post by zuzu096
I feel like I'm being really stupid with this BUT why are compounds with high oxidation states eg MnO4- oxidising agents and therefore are reduced? I thought because of their negative charge they would be oxidised and lose electrons?



Using OIL RIG, oxidising agents are themselves reduced. I see it that if a substance has a high oxidation state, they can only go to a lower oxidation state.. My teacher taught us that as oxidation states go from negative ox. states to positive, they are losing electrons, therefore if they are gaining electrons, they are going from high oxidation states to low oxidation states
Reply 84
Avatar for Claree
Claree
17
Original post by zuzu096
I feel like I'm being really stupid with this BUT why are compounds with high oxidation states eg MnO4- oxidising agents and therefore are reduced? I thought because of their negative charge they would be oxidised and lose electrons?


In a sense it is the Mn(VII) specifically which is reduced as opposed to the whole MnO4-.

Overall you could think of it as that the MnO4- would "lose electrons/negative charge " to become say Mn2+, but in doing so the Mn is reduced.

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Reply 85
Avatar for zuzu096
zuzu096
Original post by Suky
Using OIL RIG, oxidising agents are themselves reduced. I see it that if a substance has a high oxidation state, they can only go to a lower oxidation state.. My teacher taught us that as oxidation states go from negative ox. states to positive, they are losing electrons, therefore if they are gaining electrons, they are going from high oxidation states to low oxidation states


Thanks! I was not looking at it as just Mn2+ but as MnO4- as a whole!:colondollar:
Reply 86
Avatar for zuzu096
zuzu096
Original post by Claree
In a sense it is the Mn(VII) specifically which is reduced as opposed to the whole MnO4-.

Overall you could think of it as that the MnO4- would "lose electrons/negative charge " to become say Mn2+, but in doing so the Mn is reduced.

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Thank you that's made it so much clearer! I thought I had redox down, and understood it all it was just i was focusing on the whole MnO4- instead of Mn2+ by itself! :smile:
how much of unit 5 have people covered so far? we've just started ihope wefinish it before easter holidays
Original post by destinyschild
how much of unit 5 have people covered so far? we've just started ihope wefinish it before easter holidays


You can't finish it all within a week if you've just started? :I


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Reply 89
Avatar for Ascience
Ascience
How much of unit 5 have people covered on their own?


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Reply 90
Avatar for MySquishy!
MySquishy!
Original post by FutureMedic1009
You can't finish it all within a week if you've just started? :I


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I hate to tell you this but we've still got another half a term before Easter; it's just half term next week :P


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Original post by MySquishy!
I hate to tell you this but we've still got another half a term before Easter; it's just half term next week :P


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Lol sorry that was me not reading your comment properly. Ye then u should finish easily


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Reply 92
Avatar for A sheesh
A sheesh
13
Anybody else have eally bad teachers? Like ones who just skips parts out and expect us to know it?
it seems teachers cant actually be bothered teaching chem 5
Hello Everyone,

Just introducing myself into my exam threads :smile:
Does anyone have any idea what the isa grade boundaries will be like this year??
My teacher said that they will be lower but I was wondering how much lower haha


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Original post by Caribbeantwist
Does anyone have any idea what the isa grade boundaries will be like this year??
My teacher said that they will be lower but I was wondering how much lower haha


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I'm guessing low ones, as some schools are unable to cheat.


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Original post by FutureMedic1009
I'm guessing low ones, as some schools are unable to cheat.


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I hope they are lower :frown: I'm guessing As and A*s will still be 40+ though haha!
(edited 10 years ago)
Reply 97
Avatar for A sheesh
A sheesh
13
Original post by Caribbeantwist
I hope they are lower :frown: I'm guessing As and A*s will still be 40+ though haha!



In our school everybody got Us bar me and 2 others.

i got 45/50 which gave me a B 46 ums :frown:
Original post by A sheesh
In our school everybody got Us bar me and 2 others.

i got 45/50 which gave me a B 46 ums :frown:


Was this last year though? The rules have changed for this academic year and therefore no one should have done the whole isa yet as the papers are in march :smile:


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Original post by Caribbeantwist
I hope they are lower :frown: I'm guessing As and A*s will still be 40+ though haha!


I agree, I'm sure A's and A*'s will all still be up there in the 40's


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