SOLUTIONS
Chapter 11 part 3: Electrolytes
Read:
HW:
Homogeneous mixture:
BLB 4.1, 4.5; 13.4
BLB 4:3, 15, 37, 61, 71, 72, 73;
13:39, 47
Packet 4:1–3, 13:1-5
Solute:
Know:
! solutions
! electrolytes
Solvent:
Aqueous solutions:
Dr. L. Van Der Sluys
Page 1
Chapter 13 part 1
Dr. L. Van Der Sluys
hvordan å signere en autograf
Page 2
Chapter 13 part 1
Which Bulbs Light Up?
Electrolytes
Bulb Wattage
7.5
25
DEFINITION:
40
Distilled H2O
• Strong – COMPLETELY ionized(in solution)
Good conductors
Tap H2O
NaCl(s) + H2O ! Na+(aq) + Cl" (aq) + H2O
NaCl(aq)
HCl(aq) + H2O ! H3O +(aq) + Cl" (aq)
1M HCl(aq)
• Weak – PARTIALLY ionized (in solution)
Poor conductors
1M CH3COOH
sugar(aq)
NH3(aq) + H2O
NH4+(aq) + OH" (aq)
CH3OH
• For bulb to light, some minimum amount of
current is needed.
• amount of current is related to the
CONDUCTIVITY of the solution.
CONDUCTIVITY: ability to conduct electricity
Dr. L. Van Der Sluys
Page 3
Chapter 13 part 1
CH3COOH(aq)+H2O
+
CH3COO" (aq)+H3O (aq)
• Nonelectrolytes – NOT ionized in solution
Non-conductors
C6H12O6(s)+H2O ! C6H12O6(aq)+ H2O
glucose
Dr. L. Van Der Sluys
Page 4
Chapter 13 part 1
The Solution Process
a) Dissolution of an electrolyte in water
produces solvated ____________. Solvation
stabilizes the ions and prevents
recombination.
Example Problem:
Based on the results of the demo,
which one of the following is a weak
electrolyte?
a) distilled water
Example: NaCl
dissociates into ions.
b) NaCl(aq)
c) 1M HCl(aq)
d) 1M CH3COOH(aq)
e) sugar(aq)
f) CH3OH(aq)
b) Dissolution of a non-electrolyte in
water produces solvated _________________.
Example: CH3OH
does not
dissociate
Dr. L. Van Der Sluys
Page 5
Chapter 13 part 1
Dr. L. Van Der Sluys
Page 6
Chapter 13 part 1
Identifying an electrolyte
Ionic compounds:
A) Is the compound ionic or molecular?
If Ionic: it is a strong electrolyte
Note: it could be insoluble
If Molecular . . . .
B) If it is molecular, is it an acid or a base?
Yes: it is a strong or weak electrolyte
No: it is a non-electrolyte.
Examples of electrolytes (strong or weak)
Acids donate H+(aq)
Bases accept H+(aq)
Salts formed by replacing one or more
H+ of an acid with another cation
Metal + nonmetal (usually)
Eg. NaCl
K2SO4
Mg(NO3)2
NH4Cl
What can you say about the melting points
of ionic compounds?
Molecular compounds:
All nonmetals or nonmetals & metalloids.
Eg. HCl
H2O
CH3COOH
NH3
Examples of non-electrolytes:
Alcohols
Carbohydrates (sugar)
Aldehydes, ketones
Examples of WEAK electrolytes:
Weak Acids (including Carboxylic Acids)
Weak Bases (including Amines)
What can you say about the melting points
of molecular compounds?
Dr. L. Van Der Sluys
Dr. L. Van Der Sluys
Page 7
Chapter 13 part 1
Page 8
Chapter 13 part 1
Strong or weak electrolyte?
Common misconception:
"All Electrolytes are ionic compounds"
1) Assume all salts are strong electrolytes.
2) Memorize strong acids and strong bases;
all are strong electrolytes.
NOT TRUE!
• Strong electrolytes – ionic or molecular
compounds that ionize completely in
solution.
• Weak electrolytes– molecular compounds
that are partially ionized in solution.
• Nonelectrolytes – molecular compounds
that do not ionize in solution
If a compound is an acid or a base, but is
NOT one of the strong acids or bases,
what MUST it be?
Dr. L. Van Der Sluys
Page 9
Chapter 13 part 1
Dr. L. Van Der Sluys
Page 10
Chapter 13 part 1
Electrolyte Flowchart
Which one of the following is an ionic
compound?
A.
B.
C.
D.
Water soluble
Compound
H2O
NH4Cl
CH3COOH
NH3
molecular
ionic
Is it an acid?
Yes
Is HCl a molecular or ionic compound?
A. molecular
B. ionic
No
Is it a strong acid?
Yes
Strong
electrolyte
Is it a molecular base?
(eg. NH3)
no
yes
Which of the following is/are a weak
electrolyte(s)? A=WEAK, B=STRONG
HBr
Strong
Electrolyte
no
weak
electrolyte
weak
electrolyte
non electrolyte
NH4Cl
CH3CH2COOH
NH3
Dr. L. Van Der Sluys
Page 11
Chapter 13 part 1
Dr. L. Van Der Sluys
Page 12
Chapter 13 part 1
These are all water soluble compounds. Are
they strong, weak or non electrolytes?
A=WEAK, B=STRONG, C=NON
Use the Flowchart on the previous page
HCl
NaCl
CH3OH
CH3COOH
(acetic acid)
NH3
Fe(NO3)2
Ca(OH)2
Dr. L. Van Der Sluys
Page 13
Chapter 13 part 1