• Zigya Logo

    Redox Reactions
    pdf download

    Why do the following reactions proceed differently?
    Pb3O4 +8HCl --->3PbCl2 +Cl2 +4H2O
    Pb3O4 +4HNO3 --->2Pb(NO3)2 +PbO2 +2H2O

    Pb3O4 is a stoichiometric mixture of 2 mol of PbO and 1 mol of PbO2. In PbO and PbO2 the oxidation state of lead is +2 and +4 respectively. PbO2 thus behaves as an oxidising agent and therefore can oxidise Cl- ion of HCl into chlorine. Also, PbO being basic in nature, therefore the reaction
    Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O
    can be split into two reactions namely:

    (a) Acid-base reaction
         2PbO + 4HCl  →  2PbCl2 + 2H2O

    (b) Redox reaction
     +4          -1          +2    0
    PbO2 + 4HCl → PbCl2 + Cl2 +2H2O

    Since HNO3 itself is in oxidant, therefore, the reaction between PbO2 and HNO3 is not possible. However, the acid-base reaction occurs between PbO and HNO3 as:

    2PbO + 4HNO3 → 2Pb(NO3)2 + 2H2O
                                           (acid-base reaction).

    It is the passive nature of PbO2 against HNO3 that makes the reaction different from the one that follows with HCl.
    515 Views
    Answer

    Determine the oxidation number of:
    left parenthesis straight i right parenthesis space straight S space in space straight S subscript 2 straight O subscript 3 superscript 2 minus end superscript space straight S subscript 2 straight O subscript 3 superscript 2 minus end superscript space space space space space left parenthesis ii right parenthesis space Br space in space BrO subscript 4 superscript minus space space space space space space left parenthesis iii right parenthesis space straight P space in space HPO subscript 4 superscript 2 minus end superscript




    The algebraic sum of the oxidation number of various atoms  = 1
     
    The algebraic sum of the oxidation number of various atoms = 2

    100 Views
    Answer

    Determine the oxidation number of C in the following:
    bold left parenthesis bold i bold right parenthesis bold space bold C subscript bold 2 bold H subscript bold 6 bold space bold space bold space bold space bold space bold space bold space bold space bold space bold left parenthesis bold ii bold right parenthesis bold space bold C subscript bold 4 bold H subscript bold 10 bold space bold space bold space bold space bold space bold space bold space bold space bold space bold left parenthesis bold iii bold right parenthesis bold space bold CO bold left parenthesis bold iv bold right parenthesis bold space bold CO subscript bold 2 bold space bold space bold space bold space bold space bold space bold space bold space space space

    C2H6: Let the oxidation number of C= x
    Oxidation number of H = 1
    The algebraic sum of the oxidation number of various atoms = 0

           


    (ii) C4H10:
     Let the oxidation number of C = x
    Writing the oxidation number of each atom at the top of its symbol,
                               x                +1
                             C4                 H10
    The algebraic sum of the oxidation number of various atoms = 0

                     4x  + 10(+1) = 0
    or                        4x = -10

    or                         
    (iii) CO:
    Let the oxidation number of C = x
    Writing the oxidation number of each atom at the top of its symbol,
                       x               -2
                       C                O
    The algebraic sum of the oxidation number of various atoms = 0
                                       x - 2  = 0
                            or             x = 2

    (iv) CO2:
    Let the oxidation number of C = x
    Writing the oxidation number of each atom at the top of its symbol,
                   x              -2
                   C              O2

    The algebraic sum of the oxidation number of various atoms = 0

                 x + 2(-2) = 0
    or                  x = 4


                       
     
    109 Views
    Answer
    Advertisement
    Zigya App

    Which of the following species, do not show disproportionation reaction and why?
    ClO–, ClO2–, ClO3- and ClO4– 
    Also write reaction for each of the species that disproportionates.

    ClO- (hydrochlorite ion):


    ClO4-1 (perchlorate ion) cannot show any disproportionation reaction. The oxidation state of Cl is ClO4- ion is +7. It is the maximum oxidation state which it can have. It is the maximum oxidation state which it can have. It can decrease the same by undergoing reduction and not increase it anymore hence ClO4- ion does not undergo disproportionation reactions.




    679 Views
  • Switch
    • Advertisement

    What is the oxidation number of sulphur in:
    (i)H2SO4            (ii)        Na2S2O3?

    (i) H2SO4:
    Let the oxidation number of S = x
    Writing the oxidation number of each atom at the top of its symbol
    +1             x             -2
    H2             S              O4
    The algebraic sum of the oxidation number of various atoms = 0
    2(+1) + x + 4(-2) = 0
                  x - 6  = 0
                       x = +6

    (ii) Na2S2O2:
    Let the oxidation number of S = x
    Writing the oxidation number of each atom at the top of its symbol.
                   +1             x            -2
                  Na2            S2            O3
    The algebraic sum of the oxidation number of various atoms  = 0
                           2(+1) + 2(x) + 3(-2) = 0
    or                           2 + 2x - 6 = 0
                                     x = +2

    163 Views
    Answer
    Advertisement
    Flag Popup Icon
    Flag it
    Submit
    Flag Popup Icon
    Switch to
  • Type
  • Category
    • flexipad
    Share It Icon
    Share it
    Share It
    Share it