How to deal with a broken thermometer in chemistry lab ?

Isolate the lab immediately  mercury can be easily tracked throughout a lab by people walking on spill. laboratory staff can safely clean up small spill  . don't stamp on small pieces . carefully inspect the bench tops and floors before sitting. to  avoid hurting .

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.