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Pg 646 - 651. Balancing redox reactions. Balancing Redox Reaction. Can use “old” way: Ag (s) + Fe(NO3)3 ( aq ) Fe (s) + AgNO3 ( aq ) But what if we have a reaction that looks like this…. MnO4- ( aq ) + Fe2+ ( aq ) Fe3+ ( aq ) + Mn2+ ( aq ). acid. Half-Reaction Method.
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Pg 646 - 651 Balancing redox reactions
Balancing Redox Reaction • Can use “old” way: Ag (s) + Fe(NO3)3 (aq) Fe (s) + AgNO3 (aq) • But what if we have a reaction that looks like this…. MnO4- (aq) + Fe2+ (aq) Fe3+ (aq) + Mn2+ (aq) acid
Half-Reaction Method • Separate the reaction into an oxidation half-reaction and a reduction half-reaction. • Balance ANY atom that isn’t an H or O in each reaction using coefficients.
Half-Reaction Method • Balance any O’s by adding water to the opposite side of the half-reaction. • Balance any H’s by adding H+ to the opposite side of the reaction.
Half-Reaction Method • Add electrons to each half-reaction so that the charges on both sides of the reaction are the same. • Balance the total number of electrons so they are EQUAL in both reactions.
Half-Reaction Method • Add the two half-reactions together • Check to make sure the atoms and charges balance!!
Let’s try one more!! • Balance the following redox reaction using the half-reaction method: Pb (s) + PbO2 (s) + H+ (aq) Pb2+ (aq) + H2O (l)
Now you try one!! Balance the following reaction using the half-reaction method: Ni (s) + NO3- (aq) Ni2+ (aq) + NO2 (g)