1. Why upon mixing do some solutions get cold while other release heat?
EXOTHERMIC
ENDOTHERMIC
Why upon mixing do some solutions get cold while other release heat?

2. Solutions
Pure Solvent
Pure Solute
Mixture

3. When copper chloride is dissolved in water, the ions are cloaked in water molecules
Solvation

5. Heat of Solution: DHsoln
The amount of heat involved in the process of solution formation

7. DHsoln = 1in + 2out = 821 – 819 = 2 kJ/mol
Net energy (DHsoln) is the sum of the parts
2. Hydrate ions
1. Break ions apart
DHsoln = 1in + 2out = 821 – 819 = 2 kJ/mol

8. Neg. = out (h T)
Positive = in (,T)
DHsoln = DHs + DHaq

9. Heat of Solution
If the enthalpy of formation of the solution is more negative that that of the solvent and solute, the enthalpy of solution is negative.
The solution process is exothermic!

10. Energy of a System
Depends on the polarity of the solvating molecule, size of the ions and the charge
The higher the charge, the stronger the attraction (Mg+2 vs. Li+1 and K+1)
The smaller the ion, the stronger the attraction (Li+1 vs. K+1)

11. Heat of Solution: DHsoln
Determines the solubility of a substance:
If the DHsoln is very positive, water does not have enough energy to break ions apart and it will NOT dissolve
If the DHsoln is negative, water will gain energy from ions and it will dissolve

12. Hydration Energy
1. Explain why the enthalpy of hydration of Na+ is more negative than that of Cs+.
Na+ is smaller size
2. Explain why the enthalpy of hydration of Mg2+ is more negative than that of Cs+.
Mg2+ has greater charge
3. Which should have a more negative enthalpy of hydration F-or Cl- ? Explain
F- is smaller size

13. MEASRUING Heat of Solution
NH4(OH)2
The solution process is endothermic
What is the Molar
DHsoln ?
Ba(OH)2
The solution process is exothermic
What is the Molar
DHsoln ?