Consider the thermodynamics of chlorination of methane and the chlorination of ethane and use the hammond postulate to explain why one of these reactions has a much larger isotope effect than the other.

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.