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|Section8= }} Potassium hypomanganate, K3MnO4, also known as potassium manganate(V), is a bright blue salt and a rare example of a manganese(V) compound. It is formed: *by the reduction of potassium permanganate with excess potassium sulfite;〔.〕〔.〕 ::MnO + SO + H2O → MnO + SO + *by the reduction of potassium manganate with hydrogen peroxide in 10 M potassium hydroxide solution;〔.〕 :: + H2O2 + → + O2 + *by the reduction of potassium manganate with mandelate in 3–10 M potassium hydroxide solution;〔 :: + CHO + → + CHO + *by disproportionation when manganese dioxide is dissolved in a concentrated solution of potassium hydroxide;〔 :: + → MnO + MnO(OH) + H2O The hypomanganate anion is unstable with respect to disproportionation in all but the most alkaline of solutions:〔〔 estimated electrode potentials at pH 14 are〔.〕〔.〕〔.〕 :MnO + e− MnO ''E'' = +0.27 V :MnO + e− + MnO2 + ''E'' = +0.96 V The disproportionation is believed to pass through a protonated intermediate,〔 with the acid dissociation constant for the reaction HMnO MnO + H+ being estimated as p''K''a = .〔.〕 However, K3MnO4 has been cocrystallized with Ca2Cl(PO4), allowing the study of the UV–visible spectrum of the hypomanganate ion.〔〔.〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「potassium hypomanganate」の詳細全文を読む スポンサード リンク
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