Section 6.5 pg

ACIDSBASES Fill in as many empirical properties for acids and bases as you can...

Two different acids of the same concentration were tested with a pH meter. HCl(aq) 1.0 mol/L = pH = 1 CH3COOH 1.0 mol/L = pH = 4 ??? How does this happpen ???

 The concept of strong and weak acids was developed to describe and explain the differences in properties of acids.  An acid can be described as a weak acid if its characteristic properties (under the same conditions) are less than those of a common strong acid  There are relatively few strong acids: ( 6 to be exact )

 Strong Acids:  These empirical properties suggest many ions are present (lots of H 3 O + ions present); which is consistent with the idea that strong acids react completely _________ with water to form hydronium ions

 Weak Acids:  These empirical properties suggest fewer hydronium ions are present  Based on this evidence, a weak acid reacts incompletely _________ with water to form relatively few hydronium ions --

 Because of this difference, weak acids are much safer to handle – you can even eat and drink many of them. Lactic acid in many dairy products and builds up in muscles Citrus acid in fruits Stearic Acid in Animal Fat Carbonic acid in drinks Tannic Acid in Tea

 Pg. 255 #1-5

 Strong bases – have a high electrical conductivity, fast reaction rate and a very high pH (>>7)  Weak bases – have a low electrical conductivity (if molecular bases), slower reaction rate and a pH closer to, but greater than, 7  How do we explain the difference?

 Strong Bases –  Weak Bases – an ionic or molecular substance that reacts partially ________ with water to produce relatively few hydroxide ions

 Explain the weak base properties of baking soda.  Explain why sodium acetate has a pH of 8 when dissolved in water.

 Pg. 257 #6, 7, 9

Strong AcidsWeak AcidsStrong BasesWeak Bases Empirical properties (need same concentration & temperature) Very low pHMed to low pHVery high pHMed to high pH High conductivity Low conductivity High conductivity Low conductivity* Fast reaction rate Slow reaction rate Fast reaction rate Slow reaction rate Modified Arrhenius Theory Completely react with water to form H 3 O + (aq) ions Partially react with water to form H 3 O + (aq) ions Completely react with water to form OH - (aq) ions Partially react with water to form OH - (aq) ions * Applies only to weak bases that are molecular

 The evidence from the demonstration clearly shows that acids with the same initial concentration can have different degrees of acidic properties.  This difference was shown in the different conductivity measurements and the different rate of reactions.  What were the two important controlled variables? concentration and temperature  Why? A very dilute strong acid could have a higher pH than a more concentrated weak acid – which is incorrect and the conductivity and rate of reaction measurements would be misleading.