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Determine if reactions are redox

  1. Oct 14, 2015 #1
    1. The problem statement, all variables and given/known data

    Determine which is/are redox reaction/s ?
    ##1. 2HNO_2 + 2HBr \rightarrow 2NO + BR_2 + 2H_2O##
    ##2. PbO_2 + SO_2 \rightarrow PbO + SO_3##
    ##3. 2Ag + Cl_2 \rightarrow 2AgCl##
    ##4. SO_2 + NaOH \rightarrow NaHSO_3##

    2. Relevant equations
    Redox reactions are the ones which involves changes in oxidation numbers

    3. The attempt at a solution

    Since all reactions involves change in oxidation number
    1. Br
    2. Pb
    3. Cl
    4. S

    I think all the reactions are redox.
    But, the answer is just reaction 1, 2, and 3

    Please tell me why reaction 4 is not redox reaction
  2. jcsd
  3. Oct 14, 2015 #2


    User Avatar

    Staff: Mentor

    What is the oxidation number of S before the reaction? After the reaction?
  4. Oct 14, 2015 #3
    Hmm... it's +4 and +4... No change... Thankss... I missed it
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