The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained alongwith potassium nitrate solution. Gas C does not burn itself but helps burn things. (a) What is compound A? (b) What is compound B? (c) What is gas C? (d) What do you think is the black substance X? What is its function? What is the general name of substance like X?