H2O + O2 2 PbO2 + 4 HNO3 → 2 Pb(NO3)2 + 2 H2O + O2 PbO2 + 4 HCl → PbCl2 + 2 H2O + Cl2 However these reactions are slow. Lead dioxide is well known for being a good oxidizing agent, with an example reactions listed below: 2 MnSO4 + 5 PbO2 + 6 HNO3 → 2 HMnO4 + 2 PbSO4 + 3 Pb(NO3)2 + 2 H2O 2 Cr(OH)3 + 10 KOH + 3 PbO2 → 2 K2CrO4 + 3 K2PbO2 + 8 H2O Electrochemical Although the formula of lead dioxide is nominally given as PbO2, the actual oxygen to lead ratio varies between 1.90 and 1.98 depending on the preparation method. Deficiency of oxygen (or excess of lead) results in the characteristic metallic conductivity of lead dioxide, with a resistivity as low as 10−4 Ω·cm and which is exploited in various electrochemical applications. Like metals, lead dioxide has a characteristic electrode potential, and in electrolytes it can be polarized both anodically and cathodically. Lead dioxide electrodes have a dual action, that is both the lead and oxygen ions take part in the electrochemical reactions. Production Chemical processes Lead dioxide is produced commercially by several methods, which include oxidation of red lead (Pb3O4) in alkaline slurry in a chlorine atmosphere, reaction of lead(II) acetate with "chloride of lime" (calcium hypochlorite), The reaction of Pb3O4 with nitric acid also affords the dioxide: Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O PbO2 reacts with sodium hydroxide to form the hexahydroxoplumbate(IV) ion [Pb(OH)6]2−, soluble in water. Electrolysis An alternative synthesis method is electrochemical: lead dioxide forms on pure lead, in dilute sulfuric acid, when polarized anodically at electrode potential about +1.5 V at room temperature. This procedure is used for large-scale industrial production of PbO2 anodes. Lead and copper electrodes are immersed in sulfuric acid flowing at a rate of 5–10 L/min. The electrodeposition is carried out galvanostatically, by applying a current of about 100 A/m2 for about 30 minutes. The drawback of this method for the production of lead dioxide anodes is its softness, especially compared to the hard and brittle PbO2 which has a Mohs hardness of 5.5. This mismatch in mechanical properties results in peeling of the coating which is preferred for bulk PbO2 production. Therefore, an alternative method is to use harder substrates, such as titanium, niobium, tantalum or graphite and deposit PbO2