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Topic: PREDICTING REDOX REACTIONS  (Read 20424 times)

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777888

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PREDICTING REDOX REACTIONS
« on: October 22, 2004, 01:37:27 PM »
List all entities initally present (break to ions if possible) in the following mixtures and identify all possible oxidizing and reducing agents:

1) An aqueous chlorine solution is added to a phosphorous acid solution.
-Why can't H3PO3 break into ions H+, PO3(2-)??? (there is no PO3(2-) in both OA and RA side in the redox table)

2) Iodine solution is added to a basic mixture containing manganese(IV) oxide.
-Can MnO2 break into ions?

3)A potassium dichromate solution is added to an acidic iron(II) nitrate solution.
-Are these the correct entities?
K+    Cr2O7(2-)    H+    H2O    Fe(2+)    NO3(-)

Thank you!
« Last Edit: October 23, 2004, 04:57:01 PM by 777888 »
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Offline Donaldson Tan

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Re:PREDICTING REDOX REACTIONS
« Reply #1 on: October 22, 2004, 07:21:54 PM »
Quote from: Mitch on March 21, 2004, 07:43:24 PM
2.) Please don't list 5-6 homework questions and say you need help right away. It is your own responsibility to start your homework early.  If you do have a lot of questions put them in one post but don't expect them to all be answered at once. Violators will have their multiple posts deleted.

3.) Please show that you've at least attempted the problem.  We don't mind helping you solve problems but we are ethically opposed to doing homework for you.

Please refer to this link http://www.chemicalforums.com/index.php?board=4;action=display;threadid=59 for more information
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777888

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Re:PREDICTING REDOX REACTIONS
« Reply #2 on: October 22, 2004, 10:20:20 PM »
Actually, these are the questions left over that I didn't get it! I put my problem below the question!
« Last Edit: October 22, 2004, 10:47:06 PM by 777888 »
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777888

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Re:PREDICTING REDOX REACTIONS
« Reply #3 on: October 23, 2004, 05:25:02 PM »
Can someone teach me how to know that H3PO3, MnO2 are insouble? (PO3(3-) is not in the solubility table, I can only find PO4(3-) there)
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Offline Donaldson Tan

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Re:PREDICTING REDOX REACTIONS
« Reply #4 on: October 23, 2004, 06:52:46 PM »
Quote from: 777888 on October 23, 2004, 05:25:02 PM
Can someone teach me how to know that H3PO3, MnO2 are insouble? (PO3(3-) is not in the solubility table, I can only find PO4(3-) there)

solvation is spontaneous when |hydration energy| exceeds |lattice energy|
« Last Edit: October 25, 2004, 08:33:39 AM by geodome »
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777888

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Re:PREDICTING REDOX REACTIONS
« Reply #5 on: October 23, 2004, 08:59:14 PM »
When it says chlorine solution, does it mean Cl-(aq) or Cl2(aq)? Similarly, iodine solution refers to I-(aq) or I2(aq)? ???

For example,
""An aqueous chlorine solution"" is added to a phosphorous acid solution.

Thanks for your *delete me*
« Last Edit: October 23, 2004, 09:01:06 PM by 777888 »
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Offline Donaldson Tan

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Re:PREDICTING REDOX REACTIONS
« Reply #6 on: October 25, 2004, 08:31:11 AM »
aqueous chlorine solution refer to Cl2 (aq). It is actually an equilibrium mixture of chlorine, chloride and chlorate(I), because chlorine disproportionates in water. aqueous iodine exhibits similar property
« Last Edit: October 25, 2004, 08:31:40 AM by geodome »
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"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

Offline AWK

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Re:PREDICTING REDOX REACTIONS
« Reply #7 on: October 26, 2004, 01:45:34 AM »
 (PO3(3-) does not exists. H3PO3 is a diprotic acid, ie it can exchange only two protons during neutralization.
In solution of H3PO3 only (H+), H2PO3(-) and HPO3(2-) exist
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777888

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Re:PREDICTING REDOX REACTIONS
« Reply #8 on: October 26, 2004, 10:15:04 AM »
Quote from: AWK on October 26, 2004, 01:45:34 AM
(PO3(3-) does not exists. H3PO3 is a diprotic acid, ie it can exchange only two protons during neutralization.
In solution of H3PO3 only (H+), H2PO3(-) and HPO3(2-) exist

But there is only H3PO3 in my redox table, but no PO3(3-), H2PO3(-) and HPO3(2-).. But I need to copy the half reactions from the redox table for the strongest oxidizing and reducing agent. So does that mean in the question,
 "An aqueous chlorine solution is added to a phosphorous acid solution"
The species initally present would be: Cl2, H2O, H+, H3PO3 ?  
INSTEAD OF: Cl2, H2O, H+, PO3(3-) ? :help:
« Last Edit: October 26, 2004, 10:25:08 AM by 777888 »
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777888

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Re:PREDICTING REDOX REACTIONS
« Reply #9 on: October 27, 2004, 03:19:51 PM »
Quote from: 777888 on October 26, 2004, 10:15:04 AM
But there is only H3PO3 in my redox table, but no PO3(3-), H2PO3(-) and HPO3(2-).. But I need to copy the half reactions from the redox table for the strongest oxidizing and reducing agent. So does that mean in the question,
 "An aqueous chlorine solution is added to a phosphorous acid solution"
The species initally present would be: Cl2, H2O, H+, H3PO3 ?  
INSTEAD OF: Cl2, H2O, H+, PO3(3-) ? :help:
Just to make sure if I get the right idea!
« Last Edit: October 27, 2004, 03:20:11 PM by 777888 »
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Offline AWK

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Re:PREDICTING REDOX REACTIONS
« Reply #10 on: October 28, 2004, 04:31:30 AM »
H3PO3 is a weak acid, hence only a few percent of H3PO3 dissociates. Though in solution exist such a species, as Cl2 (Cl(-) HClO H3O(+),CLO(-)), H2O, H3PO3 (H3O(+) H2PO3(-)) you can assume that only Cl2 and H3PO3 exist in solution for the search in redox tables.
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