Download IB Chemistry SL – Additional REDOX Practice Problems

Name:______________________Date:_____________Period:______
PreAP Chemistry –REDOX Practice Problems
Directions: Identify with substance is undergoing oxidation and reduction. Also,
Identify the Oxidizing Agent and the Reducing Agent in each equation.
1) HNO3(aq) + H3AsO3(aq)  NO(g) + H3AsO4(aq) + H2O(l)
2) Cu(s) + HNO3(aq)  Cu(NO3)2(aq) + NO(g) + H2O(l)
3) NO2(g) + H2(g)  NH3(g) + H2O(l)
4) Cr2O72−(aq) + HNO2(aq)  Cr3+(aq) + NO3−(aq)
5)
Cr(OH)3(s) + ClO3−( aq)  CrO42−(aq) + Cl−(aq)
Name:______________________Date:_____________Period:______
PreAP Chemistry –REDOX Practice Problems
Directions: Identify with substance is undergoing oxidation and reduction. Also,
Identify the Oxidizing Agent and the Reducing Agent in each equation.
1) HNO3(aq) + H3AsO3(aq)  NO(g) + H3AsO4(aq) + H2O(l)
2) Cu(s) + HNO3(aq)  Cu(NO3)2(aq) + NO(g) + H2O(l)
3) NO2(g) + H2(g)  NH3(g) + H2O(l)
4) Cr2O72−(aq) + HNO2(aq)  Cr3+(aq) + NO3−(aq)
5)
Cr(OH)3(s) + ClO3−( aq)  CrO42−(aq) + Cl−(aq)
Name:______________________Date:_____________Period:______
RULES FOR BALANCING REDOX REACTIONS
Half Reaction Method
1. Write the unbalanced equation for the reaction.
2. Write the net ionic equation.
3. Assign oxidation numbers  if necessary.
4. Identify what is being oxidized and what is being reduced  if requested.
5. Write separate half-reactions for the oxidation process and for the reduction
processes  unless requested it is not necessary to identify which is which.
6. Balance the atoms other than H and O in each of the half reactions.
7. Balance the O atoms in each half-reaction using H2O molecules.
8. Balance the H atoms in each half-reaction using H+ ions.
9. If the reaction is being run in basic solution, then add exactly enough OH  ions to
both sides to combine with the H+ ions.
10. Add enough electrons to the side of each half-reaction with the greater positive
charge to balance the charges on each side of both half-reactions.
11. Multiply each half-reaction by the appropriate number so that the electrons lost in
one half-reaction are equal to the electrons gained in the other half-reaction  in other
words, so that the electrons cancel when the two half-reactions are added together.
12. Add the two half-reactions.
13. Cancel the terms that appear on both sides of the equation.
14. Reduce the coefficients to lowest terms, if necessary.
15. Add the spectator ions, if necessary, and balance.
16. Check the final equation to be sure that atoms are conserved, that charge is
conserved, and that all electrons have canceled.
HINT: Check oxygen first, many times if there is a problem it will
show up when the oxygen atoms do not balance.