Turn on thread page Beta

HELP! Why are hydrogen ions present in redox reactions? watch

    • Thread Starter
    Offline

    10
    ReputationRep:
    This is really puzzling me and I would really appreciate an explanation.

    Why are hydrogen ions (i.e., an acidic environment) necessary for redox reactions in which an oxyanion (such as the nitrate ion or sulphate ion) is acting as the oxidising agent?

    I've spent ages looking at the Lewis structures for the nitrate ion and its reduction product (nitrogen dioxide) and can see that an oxygen atom with one extra electron breaks off the nitrate ion. I understand that this causes the central atom in the oxyanion to be reduced because it regains control of a valence electron.

    I realise that that the oxygen atom with one extra electron will require another electron for a full octet. I understand that this would come from the reducing agent (such as sodium). I also understand that hydrogen ions would be attracted to the newly formed oxide ion to form water.

    But I don't understand why the hydrogen ions have to be there for the reaction to take place at all, or why they have to appear in the ionic half-equations in order for everything to balance.

    I feel like I'm missing something. Thank you so much to anyone who can help.
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by stardust101)
    This is really puzzling me and I would really appreciate an explanation.

    Why are hydrogen ions (i.e., an acidic environment) necessary for redox reactions in which an oxyanion (such as the nitrate ion or sulphate ion) is acting as the oxidising agent?

    I've spent ages looking at the Lewis structures for the nitrate ion and its reduction product (nitrogen dioxide) and can see that an oxygen atom with one extra electron breaks off the nitrate ion. I understand that this causes the central atom in the oxyanion to be reduced because it regains control of a valence electron.

    I realise that that the oxygen atom with one extra electron will require another electron for a full octet. I understand that this would come from the reducing agent (such as sodium). I also understand that hydrogen ions would be attracted to the newly formed oxide ion to form water.

    But I don't understand why the hydrogen ions have to be there for the reaction to take place at all, or why they have to appear in the ionic half-equations in order for everything to balance.

    I feel like I'm missing something. Thank you so much to anyone who can help.
    They don't have to be present.

    In some cases the reduction potential in acidic conditions is different to the potential in basic conditions as different products form.

    A good example of this is the reaction of the manganate(VII) ion. It is able to reduce to the Mn(II) ion in acidic conditions, but only to the Mn(IV) state in basic conditions.
    Offline

    4
    ReputationRep:
    (Original post by stardust101)
    This is really puzzling me and I would really appreciate an explanation.

    Why are hydrogen ions (i.e., an acidic environment) necessary for redox reactions in which an oxyanion (such as the nitrate ion or sulphate ion) is acting as the oxidising agent?

    I've spent ages looking at the Lewis structures for the nitrate ion and its reduction product (nitrogen dioxide) and can see that an oxygen atom with one extra electron breaks off the nitrate ion. I understand that this causes the central atom in the oxyanion to be reduced because it regains control of a valence electron.

    I realise that that the oxygen atom with one extra electron will require another electron for a full octet. I understand that this would come from the reducing agent (such as sodium). I also understand that hydrogen ions would be attracted to the newly formed oxide ion to form water.

    But I don't understand why the hydrogen ions have to be there for the reaction to take place at all, or why they have to appear in the ionic half-equations in order for everything to balance.

    I feel like I'm missing something. Thank you so much to anyone who can help.
    Basically H+ is only added to balance a reaction when it is explicitly said to take place in acidic solution. You add H+ just as you add H20, it comes out of nowhere but makes sense as the equation and ions balance but this is just based off of my knowledge I will ask my tutor and get back to you.
    Offline

    17
    ReputationRep:
    (Original post by SmyrnaGarg)
    Basically H+ is only added to balance a reaction when it is explicitly said to take place in acidic solution. You add H+ just as you add H20, it comes out of nowhere but makes sense as the equation and ions balance but this is just based off of my knowledge I will ask my tutor and get back to you.
    you're correct
    • Thread Starter
    Offline

    10
    ReputationRep:
    Thank you for this
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 14, 2017

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.