Potassium permanganate is prepared from the mineralpyrolusite, MnO_(2). Its crystals have deep purple colour. It acts as an oxidizing agentin the neutral, alkaline as well as acidicmedium. In acidicmedium , it is used in volumetric analysis for estimationof ferrous salts, oxalates etc. The titrations are carried out in presence of H_(2)SO_(4). However ,before using it as a titrant, it is first standized with standard oxalic acid solution or Mohr salt solution. In one of the experiments on titration , 13.4 g of dry pure sodium oxalate ( molar mass =134 g mol^(-1) ) was dissolvedin 100mLof distilled waterand then 100 mL of 2MH_(2)SO_(4) were added. The solution, was cooledto 25.30^(@) C. Now to this solution , 0.1 M KMnO_(4) solution was added till a very faint pink colour persisted. If of 0.1 M K_(2)Cr_(2)O_(7) solution were usedin place 0.1 M KMnO_(4) in presenceof H_(2)SO_(4) in each case, the volume of 0.1 MK_(2)Cr_(2)O_(7) solution used would be

Potassium permanganate is prepared from the mineralpyrolusite, MnO_(2)

1.	Potassium permanganate is prepared from the mineralpyrolusite, MnO_(2). Its crystals have deep purple colour. It acts as an oxidizing agentin the neutral, alkaline as well as acidicmedium. In acidicmedium , it is used in volumetric analysis for estimationof ferrous salts, oxalates etc. The titrations are carried out in presence of H_(2)SO_(4). However ,before using it as a titrant, it is first standized with standard oxalic acid solution or Mohr salt solution. In one of the experiments on titration , 13.4 g of dry pure sodium oxalate ( molar mass =134 g mol^(-1) ) was dissolvedin 100mLof distilled waterand then 100 mL of 2MH_(2)SO_(4) were added. The solution, was cooledto 25.30^(@) C. Now to this solution , 0.1 M KMnO_(4) solution was added till a very faint pink colour persisted. If of 0.1 M K_(2)Cr_(2)O_(7) solution were usedin place 0.1 M KMnO_(4) in presenceof H_(2)SO_(4) in each case, the volume of 0.1 MK_(2)Cr_(2)O_(7) solution used would be
Answer» 200 mL 400 mL 333.3 mL 666.6 mL Solution :If `K_(2)Cr_(2)O_(7)` were used, the reaction would have been `Cr_(2)O_(7)^(2-) + 16 H^(+) + 3C_(2)O_(4)^(2-) rarr 2Cr^(3+) + 7H_(2)O + 6CO_(2)` Moles of `K_(2)Cr_(2)O_(7)` required for 0.1 molof sodium oxalate `= (1)/(3) xx 0.1= 0.03333`.Hence , volume of 0.1 M `K_(2)Cr_(2)O_(7)` solution required `= 33.3mL`