March 29, 2024, 09:16:44 AM
Forum Rules: Read This Before Posting


Topic: REDOX  (Read 4957 times)

0 Members and 1 Guest are viewing this topic.

777888

  • Guest
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

  • Guest
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

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7979
  • Mole Snacks: +555/-93
  • Gender: Male
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

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
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 »
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Sponsored Links