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April 08, 2026, 10:07:41 am
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Author Topic: Iffet's chem questions:  (Read 2598 times)  Share 

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kenhung123

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Re: Iffet's chem questions:
« Reply #15 on: November 06, 2010, 08:33:35 pm »
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Water is the only product means the overall produces water only
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iffets12345

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Re: Iffet's chem questions:
« Reply #16 on: November 06, 2010, 09:37:37 pm »
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Applying Mao's tip of add OH - on this question actually works in this too :)
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98.40_for_sure

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Re: Iffet's chem questions:
« Reply #17 on: November 06, 2010, 09:41:00 pm »
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iffets yo what you get on this exam? it was frickin hard... :(
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physics

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Re: Iffet's chem questions:
« Reply #18 on: November 06, 2010, 09:43:33 pm »
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i just just did that question and got in wrong too...i dont get it.

why cant they put 2O2- --> O2   + 2e-
in the eletrochem series :(
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iffets12345

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Re: Iffet's chem questions:
« Reply #19 on: November 06, 2010, 09:44:41 pm »
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cause its not an alkaline electrolyte?
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physics

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Re: Iffet's chem questions:
« Reply #20 on: November 06, 2010, 09:49:04 pm »
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i dont get it...
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iffets12345

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Re: Iffet's chem questions:
« Reply #21 on: November 06, 2010, 10:27:10 pm »
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erm, well I don't think you can just wrench H+ ions off water.... I don't know =='
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Mao

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Re: Iffet's chem questions:
« Reply #22 on: November 06, 2010, 10:31:29 pm »
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Quote from: physics on November 06, 2010, 09:43:33 pm
i just just did that question and got in wrong too...i dont get it.

why cant they put 2O2- --> O2   + 2e-
in the eletrochem series :(

because they expect you to be able to know a reaction can only go forward when you have the reactants. In a solid oxide fuel cell, you don't have H+ therefore none of the reactions involving H+ would be possible.
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sajib_mostofa

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Re: Iffet's chem questions:
« Reply #23 on: November 06, 2010, 10:32:48 pm »
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If you use a fuel such as CH3OH and you're asked to write a reaction for a solid oxide fuel cell, how would you go about eliminating the H+?
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Mao

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Re: Iffet's chem questions:
« Reply #24 on: November 06, 2010, 10:39:04 pm »
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Quote from: sajib_mostofa on November 06, 2010, 10:32:48 pm
If you use a fuel such as CH3OH and you're asked to write a reaction for a solid oxide fuel cell, how would you go about eliminating the H+?

(1) Balance equations as per normal (acidic fuel cell)

CH3OH + H2O --> CO2 + 6H+ + 6e
O2 + 4H+ + 4e --> 2H2O

(2) Add enough base to both sides (oxide, O2-) to neutralize the acid.

CH3OH + H2O + 3O2- --> CO2 + 6H+ + 3O2- + 6e
O2 + 4H+ + 2O2- + 4e --> 2H2O + 2O2-

(3) base + acid --> water

CH3OH + H2O + 3O2- --> CO2 + 3H2O + 6e
O2 + 2H2O + 4e --> 2H2O + 2O2-

(4) cancel waters so they only appear on one side

CH3OH + 3O2- --> CO2 + 2H2O + 6e-
O2 + 4e- --> 2O2-
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sajib_mostofa

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Re: Iffet's chem questions:
« Reply #25 on: November 06, 2010, 10:45:32 pm »
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Thanks for that Mao. How does 6H+ + 3O2- give 3H2O?
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iffets12345

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Re: Iffet's chem questions:
« Reply #26 on: November 07, 2010, 12:14:07 am »
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Does anyone else find Neap papers weird? Like, not hard but they ask weird questions which are hard to get the mark for, like wayyyy to much theory on obscure things like why A is better than B as a cell/form of electricity/power supply.
There's like three in 09 .....
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