How is oxygen gas prepared from potassium chlorate? What is the role of `MnO_(2)` in this process?

Potassium chlorate on heating with cone H_2SO_4 gives

Potassium dichromate is prepared from

Oxygen gas can be prepared from solid KMnO_4 by

Describe the bulk preparation of dihydrogen by electrolytic method. What is the role of an electrolyte in this process?

6.Why does potassium carbonate can't be prepared in Solvay process?

1 gram of pyrolusite (MnO_(2)) was boiled with excess of concentrated HCl and the issuing gas was passed through a solution of potassium iodide when 1.27 g of iodide were liberated. What is the percentage of pure MnO_(2) in the sample ?