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What is the oxonium ion? watch

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    I have learnt that the oxonium ion is formed when a proton bonds to a water molecule. But how exactly does that form H3O+?
    I thought if u add a proton to water molecule you would form H2O+.
    Where does the extra hydrogen come from in the oxonium ion, because a hydrogen ion is in fact just a proton. So I don't understand why the formula of the oxonium ion is H3O+ instead of H2O+.
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    Proton = H+. So Proton + H20 = H+ + H20 = H30+..
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    (Original post by lorobolorolo)
    I have learnt that the oxonium ion is formed when a proton bonds to a water molecule. But how exactly does that form H3O+?
    I thought if u add a proton to water molecule you would form H2O+.
    Where does the extra hydrogen come from in the oxonium ion, because a hydrogen ion is in fact just a proton. So I don't understand why the formula of the oxonium ion is H3O+ instead of H2O+.
    It is all down to the chemical structure and bonding of the molecules you are talking about.

    H2O is a bent molecule, with 2 lone pairs and 2 bonding pairs of electrons around O atom.

    The lone pairs allows the oxygen in water to take up a proton (H+ contains no electrons) by a dative covalent bond, where both the bonding electrons in that particular bond comes from the oxygen. Then, the positive charge from H gets forwarded to the oxygen atom, hence where it resides in oxonium, H3O+.

    When you consider the change in structure and bonding, H3O+ contains of 3 bonding pairs and 1 lone pair of electrons around O atom. it is no longer bent as one lone pair remaining, so the repulsion is lesser than between 2 lone pairs. H3O+ now becomes trigongal pyramidal.

    In terms of equation,

    H2O + H+ ---> H3O+


    Also similar is the reaction of ammonia to take up proton to become ammonium. You can try to observe the change in structure and bonding if you sketch the respective lewis structures.
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    If I'm not mistaken an oxonium ion is a protonated ion during an acid reaction, so it is a positive ion.

    Example: Acetic acid (H3C-COOH) reacts with water, so an acetate ion and an oxonium ion (hydronium ion H3O(+)) come into being. A proton (H+) is donate to water, that's why the acetate ion is negative, while the oxonium ion is positive after reaction:

    H3C-COOH + H2O -> H3C-COO(-) + H3O(+)
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    Lets be clear, H3O+ is the 'hydronium' ion. An oxonium is an oxygen cation (positive ion). For example I have been using triethyloxonium tetrafluoroborate recently. This is an oxonium and isn't protonated water!
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    (Original post by JMaydom)
    Lets be clear, H3O+ is the 'hydronium' ion. An oxonium is an oxygen cation (positive ion). For example I have been using triethyloxonium tetrafluoroborate recently. This is an oxonium and isn't protonated water!
    Pfft I use that all the time
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    (Original post by JMaydom)
    Lets be clear, H3O+ is the 'hydronium' ion. (...)
    Yeah, you are right. That is the term which I'm used to, but it seems that Oxonium ion is another word for that which can be used, even if it is not so common than Hydronium ion.
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    Oxonium refers to any positively charged oxygen with three bonds. This could be a protonated water molecule, a protonated ether, R3O+ or a positively charged carbonyl derivative such as those formed during acetal formation.
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    It is simple primary school maths.
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    (Original post by Kallisto)
    Yeah, you are right. That is the term which I'm used to, but it seems that Oxonium ion is another word for that which can be used, even if it is not so common than Hydronium ion.
    no no, it doesn't work two ways. Oxonium and hydronium aren't interchangeable. The hydronium ion is an oxonium in the same way that sulfur is an element, it is one of a larger category. If i asked what is an element you couldn't answer with sulfur.
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    (Original post by JMaydom)
    Lets be clear, H3O+ is the 'hydronium' ion. An oxonium is an oxygen cation (positive ion). For example I have been using triethyloxonium tetrafluoroborate recently. This is an oxonium and isn't protonated water!
    +1 was about to stress this lol
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    (Original post by JMaydom)
    no no, it doesn't work two ways. Oxonium and hydronium aren't interchangeable. The hydronium ion is an oxonium in the same way that sulfur is an element, it is one of a larger category. If i asked what is an element you couldn't answer with sulfur.
    I have looked for oxonium-ions in my chemistry book and H3O(+) is depicted every time. I'm a little bit confused. Could you name an example, please?
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    (Original post by Kallisto)
    I have looked for oxonium-ions in my chemistry book and H3O(+) is depicted every time. I'm a little bit confused. Could you name an example, please?
    As I said earlier:

    (Original post by illusionz)
    Oxonium refers to any positively charged oxygen with three bonds. This could be a protonated water molecule, a protonated ether, R3O+ or a positively charged carbonyl derivative such as those formed during acetal formation.
    The hydronium ion is an example of an oxonium ion. The oxoniun ion refers to a class of positively charged, trivalent oxygen ions.
 
 
 
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