**Dougherty
Valley High Chemistry **

**Balancing Redox
Equations Practice**

**How to
Balance Redox Equations:**

- Assign
oxidation numbers to each element in the equation. Figure out which
elements have their oxidation numbers change in the reaction.
- Figure
out the oxidation number increase or decrease of the elements.
- Find
the lowest common multiple of the increase in oxidation number and the
decrease in oxidation number. Figure out what number you need to multiply
the increase/decrease in oxidation number by to get the lowest common
multiple. This number is the number of atoms of each particular element
needed on both sides of the equation. Fix the coefficients of the affected
elements.
- Balance
the rest of the equation like regular.
- You
may wish to double check your balanced redox equation by checking that the
total number of charges on either side is equal.

**Balancing
Redox Equations Practice:**

- Ag (
*s*) + HS^{-}(*aq*) + CrO_{4}^{2-}(*aq*) + H_{2}O (*l*) --> Ag_{2}S (*s*) + Cr(OH)_{3}(*s*) + OH^{-}(*aq*)

[Click for Answer to Practice Problem #1]

- AsO
_{3}^{3-}(*aq*) + Br_{2}(*aq*) + OH^{-}(*aq*) --> AsO_{4}^{3-}(*aq*) + Br^{-}(*aq*) + H_{2}O (*l*)

[Click for Answer to Practice Problem #2]

- SO
_{2}(*aq*) + Cr_{2}O_{7}^{2-}(*aq*) + H^{+}(*aq*) -- > Cr^{3+}(*aq*) + SO_{4}^{2-}(*aq*) + H_{2}O (*l*)

[Click for Answer to Practice Problem #3]

- Cl
_{2}(*aq*) + H_{2}O (*l*) --> ClO_{3}^{-}(*aq*) + Cl^{-}(*aq*) + H^{+}(*aq*)

[Click for Answer to Practice Problem #4]

Answers to these 4 practice problems are posted. Click on
the answer link to find out how to answer the problem or check your answer.