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