Heat Compress

[MedChad]

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The question is:
Which of the following solvation reactions could be used for a heat compress?

a. A rxn breaking weak lattice forces and forming strong solvent- to ion interactions
b. A rxn breaking strong lattice forces and forming strong solvent-to ion interactions
c. A rxn breaking weak lattice formation and forming weak solvent to ion interactions
d. A rxn breaking strong lattice forces and forming weak solvent to ion interactions?

this is Gen chem part 2, chap 8, passage x, # 65 in tbr. I just dont understand it conceptually and tbr's explanation didn't help me that much. Thanks in advance for the help guys.

Ill post the answer after a few replies.

 

[MedPR]

The question is:
Which of the following solvation reactions could be used for a heat compress?

a. A rxn breaking weak lattice forces and forming strong solvent- to ion interactions
b. A rxn breaking strong lattice forces and forming strong solvent-to ion interactions
c. A rxn breaking weak lattice formation and forming weak solvent to ion interactions
d. A rxn breaking strong lattice forces and forming weak solvent to ion interactions?

this is Gen chem part 2, chap 8, passage x, # 65 in tbr. I just dont understand it conceptually and tbr's explanation didn't help me that much. Thanks in advance for the help guys.

Ill post the answer after a few replies.

A heat compress? Like a hot pack for an injury or something? I would go with A since it is the most exothermic reaction.

 

[MedChad]

A heat compress? Like a hot pack for an injury or something? I would go with A since it is the most exothermic reaction.

your correct! I know it has to be a exothermic rxn., but I am thinking about it backwards I suppose. My thought process is that If your going to break weak lattice forces, than little energy is released ( exo). When you are forming strong bonds ( interactions), then your increasing the endothermic part of the rxn, which is not what were looking for. So do I just have my thought process backwards? So frustrating!!

 

[theseeker4]

your correct! I know it has to be a exothermic rxn., but I am thinking about it backwards I suppose. My thought process is that If your going to break weak lattice forces, than little energy is released ( exo). When you are forming strong bonds ( interactions), then your increasing the endothermic part of the rxn, which is not what were looking for. So do I just have my thought process backwards? So frustrating!!

The bonds are weak because they are not energeticaly favorable. It would take more energy INTO the system to break a stronger bond than a weaker bond. That means breaking the weaker bond is more exothermic than breaking the strong bond. Likewise, forming a strong bond releases more energy than forming a weak bond (or requires less energy input). The most exothermic process is A.

 

[MedPR]

your correct! I know it has to be a exothermic rxn., but I am thinking about it backwards I suppose. My thought process is that If your going to break weak lattice forces, than little energy is released ( exo). When you are forming strong bonds ( interactions), then your increasing the endothermic part of the rxn, which is not what were looking for. So do I just have my thought process backwards? So frustrating!!

Enthalpy of reaction is bonds broken minus bonds formed. If you break weak bonds and form really strong bonds, you have a large negative number = lots of heat released.

Strong bonds have higher energy than weak bonds. Don't get this confused with stability or reactivity; unstable things are at a higher energy level than stable things.