Redox stoichiometry, oxidation states

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[cyborg22]

hello, i'm going crazy with the oxidation states of the different compounds in the following problem:


We are disinfecting water with hydrochlorous acid (HOCl) before discharging it to the environment. To avoid damage to receiving waters, disinfection is followed by dechlorination, adding to water Bisulfite (HSO3-) which reacts with the excess hypoclorous acid. The reaction is:
                            HOCl + aHSO3- ---> bCl- +cSO4 2- +dX

the letters a-d represent stoichiometric coefficients and the symbol X represents a chemical element or compound.

a) give the oxidation states of the following  elements:
Cl in HOCl; S in HSO3-; S in SO42-
b)determine stoichiometric coefficients a-d
c) what is the unknown species, X, and its coefficient d?


thank you!

 

[Otis]

Assign oxidation number following the rules in your chem book. Most important but often neglected - use the rules in the order given. Do not play hop-scotch with the rules.

  1. All atoms in their elemental state are assigned zero
  2. Group 1 and 2 and other simple ions are assigned their normal charge
  3. Hydrogen is assigned 1+, except hydride is assigned 1-
  4. Oxygen is assigned 2-, except peroxide is assigned 1-
  5. The sum of the oxidation numbers must equal the net charge on the polyatomic ion or  compound.

Good luck,

Otis

Added

To balance the redox equation see my reply (#9) at http://www.mychemistrytutor.com/forums/ap-chemistry/balancing-oxidation-reduction-equations/