Thermochemistry

What’s the difference?

Enthalpy (H) Heat content of a chemical system. DH = “change in enthalpy” DH = Hproducts – Hreactants DH can be + (heat is absorbed) DH can be – (heat is released)

Predict the products: CaO + H2O  ? Ba(OH)2 + NH4Cl  ? Write your observations of the reaction. Ba(OH)2 + NH4Cl  ?

If DH is + Reaction absorbs heat. Products have higher enthalpy than reactants. Reaction is ENDOTHERMIC.

If DH is - Reaction releases heat. Reactants have higher enthalpy than products. Reaction is EXOTHERMIC.

Summary: CaO + H2O Ca(OH)2+ heat ΔH = negative, exothermic Heat + Ba(OH)2 + 2NH4Cl  BaCl2 + 2NH4OH ΔH = positive, endothermic