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    Home > Chemicals Industry > Chemical Technology > Compounds of vanadium subgroup elements

    Compounds of vanadium subgroup elements

    • Last Update: 2021-06-30
    • Source: Internet
    • Author: User
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    1.
    Oxide

    Vanadium pentoxide (V 2 O 5 ) is one of the important compounds of vanadium.
    Its color ranges from orange-yellow to deep red (generally orange-yellow), odorless, tasteless, toxic, and slightly soluble in water
    .


    V 2 O 5 is a catalyst for the oxidation of SO 2 to SO 3 for the production of sulfuric acid


    V 2 O 5 can be obtained by thermal decomposition of NH 4 VO 3 .

    2NH 4 VO 3 =V 2 O 5 +2NH 3 +H 2 O

    V 2 O 5 is an amphoteric partial acid, easily soluble in NaOH, and also soluble in strong acids with larger concentrations
    .


    V 2 O 5 is dissolved in NaOH solution to obtain nearly colorless vanadate Na 3 VO 4 or metavanadate NaVO 3 solution; dissolved in strong acid, in acidic solution with pH<1, it can produce light yellow Vanadium dioxy cation VO 2+


    V 2 O 5 is highly oxidizing and reacts with concentrated hydrochloric acid to generate chlorine gas
    .

    V 2 O 5 +6HCI=2VOCl 2 +Cl 2 +3H 2 O

    The dark blue VO 2 can be slowly reduced by V 2 O 5 , and VO 2 dissolves in acid to generate blue VO 2+
    .


    KMnO 4 reacts quantitatively with VO 2+ in acid medium


    V 2 O 3 is black, and VO is gray-black
    .


    Vanadium can also form many non-integral compounds with oxygen


    Both Nb 2 O 5 and Ta 2 O 5 are white solids, amphoteric and slightly alkaline, low in activity, and do not interact with other acids except HF
    .


    The eutectic of Nb 2 O 5 , Ta 2 O 5 and NaOH respectively generates corresponding oxo acid salts


    2.


    Oxygenates

    Vanadates include orthovanadates (such as Na 2 VO 4 ) and metavanadates (such as NaVO 3 )
    .


    N vanadate tetrahedral configuration; metavanadate VO .
    3
    - , is formed by tetrahedrally coordinated vertex co-oxo long chain structure


    VO 4 3- or VO 3 - only exists in strong alkaline solutions.


    As the pH decreases, it will gradually polymerize to form dimers (V 2 O 7 4- , colorless), trimers) V 3 O 9 3- , colorless) and decamer (V1 0 O 6 28- , orange-red) and so on


    VO 2+ can be reduced to VO 2+ by Fe 2+ , I-, etc.


    Oxalic acid can reduce VO 2+ to V 3+ , and some strong reducing agents can also reduce VO 2+ to V 2+ :

    The pentavalent vanadium solution undergoes a peroxy chain transfer reaction with H 2 O 2 and the product and color are related to the acidity and alkalinity of the solution
    .
    It produces yellow [VO 2 (O 2 ) 2 ] 3- in alkaline and neutral solutions, and mainly produces red [V(O 2 )] 3 + in strong acid solutions
    .

    3.
    Halides

    The pentahalide of vanadium is only VF 5 , and the pentahalide of niobium and tantalum can be prepared by direct combination of metal and halogen
    .
    In addition, vanadium subgroup elements can generally form tetrahalides, trihalides and dihalides
    .

    VF 5 is a colorless liquid, VF 4 is a green solid, VF 3 is a yellow-green solid, and VCl 4 is a red liquid
    .
    Saws and tantalum halides are solid, NbF .
    5
    and TaF .
    5
    as a white, NbCl5 .
    5
    , Nbl .
    5
    , TaCl5 .
    5
    and TaBr .
    5
    as a yellow, NbBr .
    5
    as an orange, Tal .
    5
    black
    .

     

     

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