Dougherty Valley High Chemistry

Balancing Redox Equations Practice

How to Balance Redox Equations:

  1. Assign oxidation numbers to each element in the equation. Figure out which elements have their oxidation numbers change in the reaction.
  2. Figure out the oxidation number increase or decrease of the elements.
  3. 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.
  4. Balance the rest of the equation like regular.
  5. 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:

  1. Ag (s) + HS- (aq) + CrO42- (aq) + H2O (l) --> Ag2S (s) + Cr(OH)3 (s) + OH- (aq)

[Click for Answer to Practice Problem #1]

 

  1. AsO33- (aq) + Br2 (aq) + OH- (aq) --> AsO43- (aq) + Br- (aq) + H2O (l)

[Click for Answer to Practice Problem #2]

 

  1. SO2 (aq) + Cr2O72- (aq) + H+ (aq) -- > Cr3+ (aq) + SO42- (aq) + H2O (l)

[Click for Answer to Practice Problem #3]

 

  1. Cl2 (aq) + H2O (l) --> ClO3- (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.