Thursday, August 1, 2019

inorganic chemistry - Sodium permanganate from manganese dioxide and sodium hypochlorite


This page states that sodium permanganate can be formed by the reaction of manganese dioxide with sodium hypochlorite and sodium hydroxide:



$$\ce{2 MnO2 + 3 NaClO + 2 NaOH -> 2 NaMnO4 + 3 NaCl + H2O}$$


I assume sodium carbonate ($\ce{Na2CO3}$) will also function in this reaction as a substitute for $\ce{NaOH}$.


Does this reaction take place at standard conditions, or are increases in temperature/pressure etc. required? Approximately how long will it take (at STP)? Also, will sodium carbonate be sufficient, or is sodium hydroxide required?



Answer



I performed this reaction, and the answer is yes, concentrated sodium carbonate can be used in place of sodium hydroxide, though the latter works better. The reaction goes under normal pressure, but it requires heating. The rate of the reaction also depends on the quality of manganese dioxide - freshly prepared works best. You will notice the formation of permanganate as soon as you boil the reaction mixture, but complete conversion of dioxide may take several minutes to hours. If you want a complete conversion, better use the sodium hydroxide.


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