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Minimising the formation of manganese dioxide in the titration of potassium permanganate
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Larry Hale
Minimising the formation of manganese dioxide in the titration of potassium permanganate
Adding a large excess of acid helps greatly as the reduction to $\ce{MnO2}$ only takes place under neutral conditions. $$\ce{2H2O + MnO4- + 3e- -> MnO2 + 4OH-}$$ Under acidic conditions the $\ce{MnO4-}$ is reduced all the way to $\ce{Mn^{2+}}$.$$\ce{8H+
+ MnO4- + 5e- -> Mn^{2+} + 4H2O}$$ Also swirling or stirring the solution as you are titrating makes a big difference as it stops the area where the permanganate is being added from becoming temporarily depleted of acid.Even if you do get some $\ce{MnO2}$ forming then as long as you have enough acid in the flask a few swirls should be enough to reduce the $\ce{MnO2}$ down to $\ce{Mn^{2+}}$.
Adding a large excess of acid helps greatly as the reduction to $\ce{MnO2}$ only takes place under neutral conditions. $$\ce{2H2O + MnO4- + 3e- -> MnO2 + 4OH-}$$ Under acidic conditions the $\ce{MnO4-}$ is reduced all the way to $\ce{Mn^{2+}}$.$$\ce{8H+ + MnO4- + 5e- -> Mn^{2+} + 4H2O}$$ Also swirling or stirring the solution as you are titrating makes a big difference as it stops the area where the permanganate is being added from becoming temporarily depleted of acid.Even if you do get some $\ce{MnO2}$ forming then as long as you have enough acid in the flask a few swirls should be enough to reduce the $\ce{MnO2}$ down to $\ce{Mn^{2+}}$.
Adding a large excess of acid helps greatly as the reduction to $\ce{MnO2}$ only takes place under neutral conditions. $$\ce{2H2O + MnO4- + 3e- -> MnO2 + 4OH-}$$ Under acidic conditions the $\ce{MnO4-}$ is reduced all the way to $\ce{Mn^{2+}}$.$$\ce{8H+ + MnO4- + 5e- -> Mn^{2+} + 4H2O}$$ Also swirling or stirring the solution as you are titrating makes a big difference as it stops the area where the permanganate is being added from becoming temporarily depleted of acid.Even if you do get some $\ce{MnO2}$ forming then as long as you have enough acid in the flask a few swirls should be enough to reduce the $\ce{MnO2}$ down to $\ce{Mn^{2+}}$.
Adding a large excess of acid helps greatly as the reduction to $\ce{MnO2}$ only takes place under neutral conditions. $$\ce{2H2O + MnO4- + 3e- -> MnO2 + 4OH-}$$ Under acidic conditions the $\ce{MnO4-}$ is reduced all the way to $\ce{Mn^{2+}}$.$$\ce{8H+ + MnO4- + 5e- -> Mn^{2+} + 4H2O}$$ Also swirling or stirring the solution as you are titrating makes a big difference as it stops the area where the permanganate is being added from becoming temporarily depleted of acid.Even if you do get some $\ce{MnO2}$ forming then as long as you have enough acid in the flask a few swirls should be enough to reduce the $\ce{MnO2}$ down to $\ce{Mn^{2+}}$.
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