Module 6

Cards (15)

Thermochemistry 
Deals with heat (energy) changes in chemical reactions
Endothermic reactions 
Reaction absorbs heat
Endothermic reactions 
Vaporization of water
Sublimation of naphthalene
Solvation of sugar in water
Endothermic reactions 
Potential energy of reactants is lower than potential energy of products, so heat is given to the reaction
Exothermic reactions 
Reaction releases heat
Exothermic reactions 
Condensation of gases
Combustion reactions
Exothermic reactions 
Potential energy of reactants is higher than potential energy of products, so excess energy is released
Enthalpy 
Total kinetic and potential energy of particles of matter
Enthalpy change 
Heat gained or lost in reactions under constant pressure
In exothermic reactions 
Enthalpy of reactants is larger than enthalpy of products, so enthalpy change is negative
In endothermic reactions 
Enthalpy of products is larger than enthalpy of reactants, so enthalpy change is positive
Enthalpy change depends on temperature and pressure, so reactions should be compared under the same conditions
Standard reference state 
Enthalpy change measured under 1 atm pressure and 25°C temperature
Thermochemical reactions 
Reactions showing both changes of matter and energy
Hess' law 
1. Sum one or more reactions to form a new reaction
2. Apply the same changes to the enthalpy changes of the used reactions