Apr 22- Ions in Solutions

On thursday's class we learned about ions in solutions.

- The formation of a solution depends on the ability of the solute to dissolve in the solvent.
- Solvation is the interacting between solutes and solvent.
- Ionic solds are crystals made up of ions (salts)
- Molecular solids are crystals made up of neutral molecules.

- Dissolving ionic solutions produces ions in a process called dissociation
Ex. NaCl(s) --(H2O)--> Na+(aq) + Cl-(aq)
- Ionization is the break up of a neutral molecule into charged particles
Ex. CH3COOH ----> CH3COO(-) + H(+)

- Determining concentrations is relatively easy.
Ex. What is the [Cl-] in a solution of 0.50M
AgCl3 ----> Ag+(aq) + 3Cl-(aq)

What is the [NO3-] in a solution of 0.82M Fe(NO3)2?
Fe(NO)3 ----> 2Fe 2+(aq) + 2NO3-(aq)
0.83M --(X2)--> 1.64M

What is the [Cr2O7 2-] and [K+] when 3.5g is dissolved in 40mL of water?
K2Cr2O7 ----> 2K(+) + Cr2O7(2-)
294.2g/mol 3.5g divided by 294.2g/mol = 0.0119mol divided by 0.04L = 0.297M

What is the [NO3-] when 100mL of 0.6M AgNO3 is mixed with 200mL of 0.40M Mg(NO3)2?"
AgNo3 ----> A3(+) + NO3(-)
0.600M 0.600M 0.600M

April 20, 2010 Class

Intermolecular Bonds
-Bonds between molecules
-3 types



1. London Dispersion Force (L.D.F)

• Results from temporary electron dipoles (2 poles)
• Weakest intermolecular force
• Increases as # e- incrase
• occurs in any compound that has e- (ie: everything)
  

2. Dipole-Dipole Force (D.D.F)

• Results from a permanent dipole in molecules
• POLAR molecules experience this force
• Polarity depends on how much elements want e-. (electronegativity)
• Electronegativity increases right and up
• The strength of a dipole-dipole bond depends on the difference in electronegativity between the 2 atoms

F-O -> lower boiling point because less electronegativity, strength of 0.5, weaker bonds
F-N -> higher boiling point because more elecronegativity, strength 1.0, stronger bonds


3. Hydrogen Bonds (H-Bonds)

• This is a special type of dipole-dipole bond between H and O, F, or N
• Any molecule that has stronger bond with larger electronegativity difference

H-F
H-O-
HN=

Identify the substances with H-Bonds:
1. CH4 -No
2. CH30H -Yes
3. H2S -No
4. CH3-NH2 -Yes (2)
5. HCl -No
6. Yes (3)

Example: Compare the boiling Points of:
4.Ethanol(C2H5OH), 26 e- (strongest) Actual = 78
2. Ethane (C2H6), 18 e- Actual = -89
3. Methanol (CH3OH), 18 e- Actual= 65
1. Methane (CH4), 10 e- (weakest) Actual = -161

Friday April 16, 2010 Class

Polar and Nonpolar Solvents/solutes
Polar Substances have an unequal distribution of charges:


Non-polar substances have unequal charge distribution (if symmetrical)