2.18     describe the laboratory preparation of oxygen from hydrogen peroxide

Hydrogen  peroxide  solution  decomposes to oxygen and water.  The reaction is very slow, so  solid  manganese (IV)  oxide  (MnO2)  is added, which  catalyses  the decomposition reaction:

2H2O2(aq) → 2H2O(l) + O2(g)

Notice that the equation doesn’t include the catalyst.  A catalyst is neither a reactant or a product, so don’t try to write it in the equation (see section 4.17 and 4.18)

Apparatus similar to that on the next page is used to collect the oxygen.