Chemistry student in need of enthalpy help!!

[futureless]

Hey, I was learning about the enthalpy of hydration today and it went *whoosh* right over my head. Have a look at this paragraph from my textbook

 

"For ions to dissolve in water they need to be seperated from one another. The ions in an ionic lattice are attracted by strong forces, so separating them is an endothermic process. For any compound to dissolve in water, a large amount of energy is needed to compensate for this endothermic change. Part of the energy is released when the ions become surrounded with water molecules. Ions and water molecules are attracted to each other so this process releases energy."

 

Erm okay, I have several questions

 

 

• Why is energy released when a bond is formed?
  
• How does the attraction of water molecules to ions release energy?
  
• Is hydration where water molecules break down a lattice by attraction and then water molecules end up surrounding a single ion OR is this solvation OR a special water case of solvation?
  
• Whats the difference between the enthalpy of solvation, the enthalpy of solution and the enthalpy of hydration?
  
• The paragraph says "Part of the energy is released...", so there's still some of the energy still needed, where does this come from?
  

 

 

As you can prabably tell, I'm totally confused and I'd appreciate any help you can give, thanks

[hotcommodity]

 

• Why is energy released when a bond is formed?
  
• How does the attraction of water molecules to ions release energy?
  
• Is hydration where water molecules break down a lattice by attraction and then water molecules end up surrounding a single ion OR is this solvation OR a special water case of solvation?
  
• Whats the difference between the enthalpy of solvation, the enthalpy of solution and the enthalpy of hydration?
  
• The paragraph says "Part of the energy is released...", so there's still some of the energy still needed, where does this come from?
  

 

 

As you can prabably tell, I'm totally confused and I'd appreciate any help you can give, thanks

 

* When the attractions of ions are strong, energy is released in their formation. We call the energy related to the formation of a lattice structure its lattice energy, and these energies are always negative because they give off energy when formed.

 

*Water molecules are very polar, which is to say the molecules have both partial positive and partial negative areas. When ions are placed into the water, these partial positive and negative areas of the water molecules attract the partial negative and positive areas of the ionic compound, respectively. When the bonds are broken, energy is released.

 

*In the case above, water is the solvent, and therefore when the water molecules break up and surround the ions that once were the ionic compound, we call it hydration. Hydration is just a specific case of solvation that implies water is the solvent.

 

*Heat of solution is the energy involved in breaking up these ionic compounds we're speaking of. In other words, its the heat that accompanies the dissolution process. The heat of solvation is just the heat of solution plus the crystal lattice energy that was mentioned above. The heat of hydration is the heat of solvation, only it implies that we're using water as the solvent.

 

*Energy is released whenever bonds are broken in the dissolution process. I'm not exactly sure what your book means by part, but they may be refering to the fact that not all of the ionic bonds are broken, reactions dont always go to 100% completion.

 

I hope that helps.

[badmen4life]

That is completely wrong, lattice energy does not exist formally. In addition to this energy released is never "negative" as negative energy would be taking us back through he abyss of time. When I completed my PhD at Cambridge University I discovered the new theorem that energy does not exist. Please do not hesitate to contact my fellow graduate Dr Bill Jones.

 

Dr William Jones

Materials Chemistry Group

Sidney Sussex College

Telephone: 01223 336468

E-mail: wj10@cam.ac.uk

[hotcommodity]

That is completely wrong, lattice energy does not exist formally. In addition to this energy released is never "negative" as negative energy would be taking us back through he abyss of time. When I completed my PhD at Cambridge University I discovered the new theorem that energy does not exist. Please do not hesitate to contact my fellow graduate Dr Bill Jones.

 

Dr William Jones

Materials Chemistry Group

Sidney Sussex College

Telephone: 01223 336468

E-mail: wj10@cam.ac.uk

 

When crystal lattices are formed, they release heat, and therefore theres a negative energy value associated with the solid. All crystal lattice energy indicates is the strength of attraction within the solid. And since when does energy not exist? Feel free to expand those thoughts in the pseudoscience sub-forum.

[chemhero]

When crystal lattices are formed, they release heat, and therefore theres a negative energy value associated with the solid. All crystal lattice energy indicates is the strength of attraction within the solid. And since when does energy not exist? Feel free to expand those thoughts in the pseudoscience sub-forum.

 

I agree. I think this other guy is just being pedantic; the negative implies the direction of energy flow with repesct to that object; i read the term negative energy being loss of energy i.e. energy given out

 

And I'm skeptical of the idea that "energy dosnt exist" too...

 

Matt