I think the correct answer would be the second option. Enthalpy change can be determine for a reaction in an aqueous solution by knowing the specific heat of the reactants. You can use the equation H = mC(deltaT) where m is the mass, C is the specific heat and (deltaT) is the change in temperature.
How can the enthalpy change be determined for a reaction in an aqueous solution? By mixing the reactants in a calorimeter and measuring the temperature change By knowing the specific heat of the reactants By knowing the mass of the reactants The enthalpy change for this type of reaction cannot be determined.