Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
Sodium Carbonate dissolving in water
Does this cause a temperature change, if so why?
If not when does this occur through dissolving salts and why?
|
|
|
Molecular Manipulations
Hazard to Others
Posts: 447
Registered: 17-12-2014
Location: The Garden of Eden
Member Is Offline
Mood: High on forbidden fruit
|
|
I'll let you look up the 'if' but I'll explain the 'why or why not'.
If a salt dissolves exothermically that means the solvant-solute van der Waals force (polar water's attraction to the polar ions) is stronger than the
solute-solute van der Waals force (the crystal's lattice, or the polar ions attraction to each other). If it dissolves endothermically then the
solute-solute force is stronger.
-The manipulator
We are all here on earth to help others; what on earth the others are here for I don't know. -W. H. Auden
|
|
|
Amos
International Hazard
Posts: 1406
Registered: 25-3-2014
Location: Yes
Member Is Offline
Mood: No
|
|
This sounds like a question off a chemistry worksheet rather than scientific inquiry...
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Yttrium2  | Does this cause a temperature change, if so why?
If not when does this occur through dissolving salts and why? |
Dissolving salts is two processes.
1) Breaking all the ionic bonds in the lattice. That's known as the Lattice Energy.
2) Solvation: interaction between the solute's ions and the solvent's molecules releases energy.
Which of both is the largest determines whether the dissolution is exothermic or endothermic.
Dissolution also ALWAYS increases Entropy (probability) of the system. That's why Endothermic dissolutions can still proceed: ΔG = ΔH - TΔS, as
long as - TΔS is more negative than ΔH, ΔG < 0 and the dissolution is thermodynamically favourable.
|
|
|
Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
I don't think I quite learned about this in Gen Chem 1, hopefully it is in Gen chem2
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
