So for the calorimetry problem with the chemical reaction, if Zn had 2 moles in the chemical equation then would you divide -159.7J/mol by 2 or is it still the same?
Also, if the system is endothermic then Delta H is positive and if system is exothermic then Delta H is negative (and vice versa for surroundings)?
Using the calorimetry example the way it was set up you end up with delta H per mole because we divide the delta H value by total moles Zn reacted. If there was a 2 multiplying the Zn in the balanced equation then you would multiply our value by 2 for the complete, balanced thermochemical equation. The fact that the coeeficient is actually 1 means that our per mole value of delta H is also the delta H per mole of reaction. Thank you for the question. I really appreciate it.
chemdoctor 
So for the calorimetry problem with the chemical reaction, if Zn had 2 moles in the chemical equation then would you divide -159.7J/mol by 2 or is it still the same?
Also, if the system is endothermic then Delta H is positive and if system is exothermic then Delta H is negative (and vice versa for surroundings)?
Hello Nofil,
Using the calorimetry example the way it was set up you end up with delta H per mole because we divide the delta H value by total moles Zn reacted. If there was a 2 multiplying the Zn in the balanced equation then you would multiply our value by 2 for the complete, balanced thermochemical equation. The fact that the coeeficient is actually 1 means that our per mole value of delta H is also the delta H per mole of reaction. Thank you for the question. I really appreciate it.