Re: what is the order of reaction for hydrogen peroxide

First we need to nail down exactly what we mean by "order".  The order of
the reaction is not determined by concentration; rather, it is how much of
an effect the concentration of a species has on the reaction that 
determines the order.

Here is the reaction you are studying:

2 H2O2 -----(I-)-----> 2 H2O   +    O2

Iodine does not show up in the overall equation, as it is a catalyst.
Its concentration, however, is still important to the overall rate.

The rate equation can't be determined just by looking at the equation.
It must be determined experimentally.  Ira Levine in "Physical Chemistry"
(2nd edition) obligingly provides it for us:

r = k[H2O2][I-]

The 'overall order' of the reaction is determined by adding up the
superscripts on each component; here, each one is equal to 1.  If the
reaction depended only on the peroxide concentration, the rate equation
would be 

r = k[H2O2]   and the reaction would be first order.   

The reaction depends on *both* concentrations, though, and neither 
concentration term is raised to any power other than 1.  Thus, this is
a second-order reaction.