To calculate the enthalpy change for the reaction 2H2O2 aq 2H2O l + O2 g , we can use Hess's Law. Hess's Law states that the enthalpy change of a reaction is the same whether it occurs in one step or several steps. We can use the given reactions to create a pathway to the desired reaction.Given reactions:1 2H2O l + 105.2 kJ 2H2 g + O2 g 2 2H2 g + O2 g 2H2O2 aq + 484.4 kJWe want to find the enthalpy change for the reaction:3 2H2O2 aq 2H2O l + O2 g First, we need to reverse reaction 1:1' 2H2 g + O2 g 2H2O l - 105.2 kJNow, we can add reaction 1' and reaction 2 to get the desired reaction:1' 2H2 g + O2 g 2H2O l - 105.2 kJ2 2H2 g + O2 g 2H2O2 aq + 484.4 kJ----------------------------------------------3 2H2O2 aq 2H2O l + O2 g + 484.4 - 105.2 kJThe enthalpy change for the desired reaction is:H = 484.4 kJ - 105.2 kJ = 379.2 kJ