Download Which Bulbs Light Up?

Which Bulbs Light Up?
Bulb Wattage
7.5
25
Based on the results of the
experiment, which one of the
following is a weak electrolyte?
40
Distilled H2O
a) Distilled H2O
Tap H2O
b) NaCl(aq)
NaCl(aq)
c) 1M HCl(aq)
1M HCl(aq)
d) 1M CH3COOH
1M CH3COOH
e) sugar(aq)
sugar(aq)
f) CH3OH
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
Identifying an electrolyte
Electrolytes
• Strong – completely ionized (in solution)
Good conductors
−
NaCl(s) + H2O → Na+(aq) + Cl (aq) + H2O
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.
−
HCl(aq) + H2O → H3O +(aq) + Cl (aq)
• Weak – partially ionized (in solution)
Poor conductors
−
NH3(aq) + H2O ↔ NH4+(aq) + OH (aq)
CH3COOH(aq)+H2O ↔ CH3COO−(aq)+H3O (aq)
+
• Nonelectrolytes – not ionized in solution
Non-conductors
C6H12O6(s)+H2O → C6H12O6(aq)+ H2O
glucose
A) Is the compound ionic or molecular?
Ionic: it is a strong electrolyte
Note: it could be insoluble
Molecular ???
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
Examples of non-electrolytes:
Alcohols
Carbohydrates (sugar)
Aldehydes, ketones
Difference between strong and weak
electrolytes
Assume all salts are strong electrolytes.
Memorize strong acids and bases
(Table 4.2)
If a compound is an acid or a base, but NOT one
of the strong acids or bases, then it MUST be a
weak electrolyte.
These are all water soluble compounds. Are
they strong, weak or non electrolytes?
Use Flowchart
HCl
NaCl
CH3OH
Common misconception:
Electrolytes are ionic compounds
CH3COOH
(acetic acid)
NOT TRUE
NH3
• Strong electrolytes – ionic or molecular
compounds that ionize completely in
solution.
Fe(NO3)2
Ca(OH)2
• Weak electrolytes– molecular compounds
that are partially ionized in solution.
• Nonelectrolytes – molecular compounds
that do not ionize in solution
Water soluble
Compound
molecular
ionic
Is it an acid?
Yes
No
Is it a strong acid?
Yes
Strong
electrolyte
Is it a molecular base?
(eg. NH3)
no
yes
Strong
Electrolyte
no
weak
electrolyte
weak
electrolyte
non electrolyte