CHEM 11 A

Monday, April 26, 2010 6:38 PM

Ions in Solutions

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

-Molecular solids are crystals made up of neutral molecules
-Dissolving ionic solutions produces ions in a process called dissociationNaCl(s)-->Na(aq)+(+)Cl(aq)-
-Ionization is the break up of a neutral molecule into charged particles
CH3COOH-->CH3COO-(+)H+

Example:Write the dissociation equations:
1)FeCl3-->Fe3(aq)+(+)3Cl(aq)-
2)Ag2O-->2Ag(aq)+(+)O(aq)2-
3)Na3PO4-->3Na(aq)+(+)PO4(aq)3-
4)(NH4)2SO4-->2NH4(aq)+(+)SO4(aq)2-

Determining concentrations is relatively easy

Example:
Q:What is the [Cl-] in a solution of 0.50M AgCl3?
A:AgCl3-->Ag(aq)+(+)3Cl(aq)-
[Cl-]=0.50Mx3
[Cl-]=1.50M

Q:What is the [NO3-] in a solution of 0.82M Fe(NO3)2?
A:Fe(NO3)2-->Fe(aq)2+(+)2NO(aq)3-
[NO3-]=0.82Mx3
[NO3-]=1.64M

Q:What is the [Cr2O72-] and [K+] when 3.5g K2Cr2O7 is dissolved in 40mL of water?
A:K2Cr2O7-->2K+(+)CrO72-
K2Cr2O7=294.2g/mol
3.5g/294.2g/mol=0.0119mol/0.040L=0.297M

Q:What is the [NO3-] when 100mL of 0.6M AgNO3 is mixed with 200mL of 0.40M Mg(NO3)2?
A:AgNO3-->Ag+(+)NO3-
C1V1=C2V2
Ag+->(0.600M)(0.100M)=C2(0.300M)
C2=0.200M
[NO3-]=(0.600mol/L)x(0.100L)=0.06mol

Mg(NO3)2-->Mg2+(+)2NO3-
C1V1=C2V2
Mg2+->(0.400M)(0.200M)=C2(0.300M)
C2=0.266M
2[NO3-]=(0.400M)x(0.200L)=0.08mol

C=0.22mol/0.3L=0.73M

6:10 PM

Intermolecular Bonds

-bonds between molecules

3 types:
1.London Dispersion Force(L.D.F.)
-Results from temporary electron dipoles
-Weakest intermolecular force
-Increases as number electrons increase
-Occurs in any compound that has electrons(i.e.everything)

2.Dipole-Dipole Force
-Results from a permenant dipole in molecules
-Polar molecules experience this force
-Polarity depends how much elements want electrons(electronegativity)
Electronegativity increases right and up
-The strength of a dipole-dipole bond depends on the difference in electronegativity between the 2 atoms

Example:
Substance, Boiling Point, # of electrons
N2, -196 C, 14
O2, -183 C, 16
NO, -152 C, 15
ICl, 97 C, 70
BR2, 59 C, 70

3.Hydrogen Bonds(H-Bonds)
-This is a special type of dipole-dipole bond between H and O, F, N
-Any molecule that has: H-F, H-O, or H-N

Example:
Identify the substances with H-Bonds
1.CH4
2.CH3OH-->H-bonds
3.H2S
4.CH3-NH2-->H-bonds
5.HCl

Compare the Boiling Point of:
Ethanol(C2H5OH-4
Ethane(C2H6)-2
Methanol(CH3OH)-3
Methane(CH4)-1

Tuesday, April 20, 2010 11:15 AM

This class was spent doing a lab on polar and non- polar solvents.
The purpose of this lab was to fnd out if glycerin is polar or non- polar.
The procedure was as followed:
-get 6 test tubes and divide them into 3 groups.
-one test tube from each group was filled with water while the other was filled with paint thinner.
-the first group had salt dissolved in it, the second group had sugar, and the third had iodine crystals.
-each tube had a stopper and was shaken to mix the solute and solvent.
-then we recorded our observations.

Monday, April 19, 2010 10:20 PM

-Charged ions are needed in solutions in order to conduct electricity.
-Ionic solutions dissociate when they are placed in water.
Ex. H2SO4---> 2H+SO4
-Molecular solutions do not usually split into ions
Ex. C12H22O11---> C12H22O11

STEPS TO DETERMINE IF SOMETHING IS CONDUCTIVE:

Metal?
Yes: No:
Conductive Solid metal?
Yes: No:
Non-Condictive Acid or Base?
Yes: No:
Conductive Ionic?
Yes: No:
Conductive Non-Conductive