Ion Effects Flashcards
What are salts
Ionic solids that dissociate in water completely
Some salts show acid base properties
Is one ion in a salt is acidic and the other is basic, how is acidity determined
If Ka >kb then it’s acidic
If kb>Ka then it’s basic
In a strong acid and strong base equation what happens if:
Mol acid>mol base
Acid =base
Base>acid
Acidic (limiting OH)
Neutral
Basic (limiting H)
In a weak acid and strong base equation what happens if:
Mol acid>mol base
Acid =base
Base>acid
Acid and conjugate base are present (buffer)
Only conjugate acid is left (OH reacted with HA completely)
Basic (excess OH)
In a strong acid and weak base equation what happens if:
Mol acid>mol base
Acid =base
Base>acid
Acidic
Only BH (conjugate acid) is present
Base and conjugate acid are present (buffer)
What is the common ion effect
What reaction is it found in
It relates to solutions where one ion involved in equilibrium arises from two sources
Titrations and buffers
What is a buffer
What does it need to be a buffer
A solution that resists changes to in pH after the addition of acid or base
Needs a conjugate acid/base pair and both need to be present in significant concentrations (0.01 to 1M)
How can buffers be made
Mixing weak acid/base and salt of its conjugate base/acid
Mixing a weak acid/base and a insufficient amount of a strong base/acid
What is the optimum range for a buffer
The Pka of the conjugate acid (+- 1)
When does a buffer work best
When the concentration of acid and its conjugate base are roughly equal
What happens when [acid]=[base] in a buffer
The pH = pKa of the conjugate acid
What is the buffer capacity, how is it determined
How much H or OH the buffer can tolerate
Found by the actual concentrations in solution
How is buffer pH determined
By the Ka of the acid
And ratio of [acid]/[base]
Slide 10 lec 20
