Hello: I am having some trouble relating to the following question to the concept of oxidation numbers as required by my practice problem, and would appreciate any help. Thank you! --- 1. Explain why it is dangerous to grind a mixture of Al with KClO4 in a mortar and pestle. --- I calculated the oxidation numbers for each element: Al = 0, K = +1, Cl = +7, and O = -2. I know that aluminium + potassium perchlorate would produce flash power through an explosive reaction, and that powdered Al would have much more surface area on which the reaction could take place. The mortar and pestle additionally would cause the reaction to occur at a faster rate since there is more contact between the particles, but I do not see how I can apply the concept of oxidation numbers to this reaction.