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Balancing Redox Reactions 2 (Worksheet)

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Section: _____________________________

Student ID#:__________________________

Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

The half-equation method separates the oxidation and reduction of a redox reaction in half reactions. Overall scheme for the half reaction method:

  • Step 1: Split reaction into half-reactions (reduction and oxidation)
  • Step 2: Balance the charge or oxidation number with electrons
  • Step 3: Balance \(O\) by adding \(H_2O\)
  • Step 4: Balance \(H\) by adding \(H^+\)
  • Step 5: Multiply by some integer to make electrons (lost) = electrons (gained)
  • Step 6: Add half equations and cancel substances on both sides
  • Step 7: (only in basic solution): add \(OH^-\) and cancel \(H_2O\)
  • Step 8: Check atom balance and charge balance on both sides of the equation!

Q1

Complete and balance the following redox reactions using the half-equation method:

\(Zn_{(s)} + H^+_{(aq)} \rightarrow Zn^{2+} + H_{2\,(g)}\) (acidic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

Q2

\(I^-_{(aq)} + {NO_2}^-_{(aq)} \rightarrow I_{2\,(s)} + NO_{(g)}\) (acidic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

 

Q3

\({MnO_4}^-_{(aq)} + Cl^-_{(aq)} \rightarrow Mn^{2+}_{(aq)} + Cl_{2\,(g)}\) (acidic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

 

Do the same reaction in basic solution:

______________________________________________________ (overall)

 

Q4

 \(Br_{2\,(l)} \rightarrow {BrO_3}^-_{(aq)} + Br^-_{(aq)}\) (basic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

Q5

 \(CrO_4^- + S^{2-} \rightarrow Cr^{3+} + SO_4^{2-}\) (acidic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)

Q6

\(H_2O_2 + NO_2^- \rightarrow H_2O + NO_3^-\) (acidic solution)

______________________________________________________ (reduction)

______________________________________________________ (oxidation)

______________________________________________________ (overall)