Hess's Law

[Cecilia Jardon 1I]

For Hess's Law do you essentially just manipulate both equations to get the equation that you need and then add both enthalpies?

[Schuyler_Howell_4D]

Pretty much. You can add (or subtract) equations together to get the desired reaction that you need the enthalpy for. Once you have decided what needs to be added or subtracted you use their enthalpies, making sure the signs match if that equation is endo- or exothermic.

[Sarah Zhao 4C]

Yep, and you can multiple the reaction coefficients and reverse the reaction so they cancel out. Just make sure you do the same to the enthalpy, respectively, multiple them or change the sign.

[Chloe Likwong 2K]

Remember to also make sure that the states are the same if you're cancelling.

[yuetao4k]

Yes, make sure that all states of matter can cancel out and then manipulate each equation (multiplying or flipping) so that you get the final equation. Add together the enthalpies to find the enthalpy of the reaction.

[maldonadojs]

Yes that is the basics. The two strategies are to either flip the equations or multiply them by whole numbers. If you do decide to flip the equation you must make sure that you change the sign of the enthalpy. (I believe that is how you spell it)