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Topic: REDOX  (Read 4942 times)

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777888

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REDOX
« on: October 27, 2004, 04:25:32 PM »
I have some questions! Hope someone can help me :) Thank you

1)"An aqueous chlorine solution is added to a phosphorous acid solution"

Would the species initally present be: Cl2, H2O, H+, H3PO3 ?  
INSTEAD OF: Cl2, H2O, H+, PO3(3-) ?
Becuase I can't find PO3(3-) in the redox table.



2)Question: Gold is added to an hydrochloric acid solution. Predict the redox reaction and determine if it's spontaneous.

Steps:
Species initally present: Au  H+  Cl-    H2O

By choosing the strongest reducing/oxidizing agents, and add the half-reactions together, I got the equation:

4H(+) +2H2O->2H2+O2+4H(+)  
2H2O->2H2+O2    Subtract  4H(+) from both sides.

Problem: Would this be spontaneous?? How can I know this by the equation? (There's only 1 reactant in the net equation so I don't know how to determine which is oxidizing agent and which is reducing agent...)

3)Would the Cu-Fe cell's(Cu and Fe as electrodes, CuCl2, FeSO4 as electrolytes, and the salt bridge contains KNO3) cell potential be 0.34-(-0.44)=0.78 V?
« Last Edit: October 27, 2004, 04:40:31 PM by 777888 »

bg1047

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Re:REDOX
« Reply #1 on: November 18, 2004, 10:15:31 PM »
Phospohric acid is HPO4(3-) not HPO3(3-).

To determine if it is spontaneous calculate the Delta G for the RXn and if it in Negative it is spontaneous.

Offline AWK

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Re:REDOX
« Reply #2 on: November 19, 2004, 03:51:19 AM »
Chlorine will oxidise phosporous acid to phosphoric acid.
H3PO3 is a diprotic acid and PO3(3-) does not exist.
« Last Edit: November 19, 2004, 08:00:09 AM by AWK »
AWK

Offline Donaldson Tan

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Re:REDOX
« Reply #3 on: November 19, 2004, 07:23:48 AM »
H3PO3 is dibasic in virtue of its structure:

                H
                |
            O=P(O-H)2

Only the hydrogen attached to the oxygen atoms are capable being released into solution as H+

For your gold question, just work out Ecell. It should be negative, ie. the reaction isn't spontaneous, because gold is less reactive than copper with bronsted acid.
« Last Edit: November 19, 2004, 07:27:10 AM by geodome »
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