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What is the difference between heat of solution and heat of reaction?
I have a lab where we are determining heat of reaction for 3 reactions + determining the heat capacity of our calorimeter. For some reason we use Tmix, the temperature at which the two substances instantaneously reacted, for Tfinal (change in temp = tfinal - tinitial) instead of the point where our temperature leveled out. I am a assuming that this is because heat of reaction is the change of enthalpy instantaneously vs heat of solution where it is the change of enthalpy until fullydilute right?
1 Answer
- biire2uLv 77 years ago
The heat of formation is defined as the amount of heat added or subtracted from the reaction at 25° C and at one atmosphere pressure when one mole of a compound is formed from its constituent elements.
In other words you are reacting a mole of the reactants at 25C and seeing if the reaction gets colder (endothermic) or releases heat (exothermic)
Heat of solution is related directly to how much energy it takes or releases to dissolve a substance into a solvent.
This energy can take place in three steps:
1) Breaking solute-solute attractions (endothermic), for instance lattice energy in salts.
2) Breaking solvent-solvent attractions (endothermic), for instance that of hydrogen bonding
3) Forming solvent-solute attractions (exothermic), in solvation.
The value of the heat of solution is the sum of these individual steps
