Answer:
The Old Thermodynamist says:
Manganese dioxide does not react with hydrogen peroxide, it acts as a catalyst in the decomposition of hydrogen peroxide into water + oxygen.
The word equation is:
Manganese dioxide + hydrogen peroxide = manganese dioxide + water + oxygen
The real equation is:
MnO2 + H2O2 = MnO2 + H2O + 0.5O2(g)
Change in Free Energy: ΔG(20C) = -116.1kJ (negative, so the reaction runs)
Change in Enthalpy: ΔH(20C) = -98.0kJ (negative, so the reaction is exothermic)