Is there a complete list of all the half equations for $\ce {H2O2}$ - both oxidation and reduction, in acidic and alkaline conditions? I've looked on the internet but can't seem to find a list with all of them.
redox - Half equations for H2O2 for its reducing and oxidising nature ...
Like all other peroxides, hydrogen peroxide ($\ce {H2O2}$) also consists of a relatively weaker $\ce {O-O}$ bond, which is susceptible for light or heat. In the presence of light (the UV light from the sun catalyzes the reaction), $\ce {H2O2}$ spontaneously decomposes into water and oxygen.
My previous understanding was that $\ce {H2O2}$ spontaneously dissociates into $\ce {H2O + O2}$, including in water. I had imagined this would have no effect on the $\mathrm {pH}$ of the water its added to. The link above says if the water is acidic, $\ce {H2O2}$ will dissociate into hydronium + hydroperoxide ($\ce {H3O+ + HOO-}$).
Adding H2O2 in water does what to the pH of the water?
These ions are necessary to react with copper and hydrogen peroxide $\ce {H2O2}$. Indeed metallic copper reacts with hydrogen peroxide $\ce {H2O2}$ and an acid in the following way : $$\ce {Cu + H2O2 + 2 H+ -> Cu^ {2+} + 2 H2O}$$ So whatever the acid chosen, hydrochloric or citric, the copper will be dissolved the same way.
The equations $ (1)$ and $ (21)$ shows that $\ce {H2O2}$ can undergo spontaneous self-oxidation-reduction, and is therefore, thermodynamically unstable. Accordingly, $\ce {H2O2}$ decomposes spontaneously and exothermically, but slowly to oxygen and water at room temperature.
How does KI catalyze the reaction with H2O2? - Chemistry Stack Exchange