Textbook Problem 4.D.9

[Joanne Sarsam 2F]

Hi,

This problem asks to solve for the the enthalpy density of the reaction. I calculated the correct number, but the reaction was exothermic so my enthalpy density answer was negative. However, the answer key lists it as a positive value. Why is this so?

Thanks for the help!

[Chem_Mod]

When calculating the enthalpy density, we really only care about energy per unit volume, or energy per liter. We are not so concerned about whether the energy is given off or taken in by the reaction. That is why the negative sign is ignored even though the reaction is exothermic.