Suppose a sample of aluminum is placed in a 25 mL graduated cylinder containing 10.5 mL of water. The level of the water rises to 13.5 mL. If aluminum's density is 2.70 g/mL, what is the mass of the aluminum?

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.