4. Acids And Bases Flashcards
What is the bronsted and Lowry explanation of acids and bases?
Aid can donate a proton and base can accept a proton
What is a conjugate base?
The base formed when a bronsted acid donates H+
What is a conjugate acid?
Acid formed when a bronsted base accepts H+
How can you use strength of acids/bases to predict direction of reactions?
stronger acid and stronger base —> weaker base and weaker acid
What is the definition of a strong acid?
Dissociates completely in water
What is meant by a weak acid?
Incomplete dissociation
Equilibrium established
How is acid strength related to K?
Larger Ka implies a stronger acid
What is the difference between a strong and weak base?
Strong bases dissociate completely in water while weak bases have incomplete dissociated, eqm established
How is Kb related to base strength?
Larger kB—> stronger base
What is the dissociation constant for water?
kw=[H3O+][OH-}
=1.00x10^-14
What is pH?
pH= -log10[H3O+]
What is pOH?
pOH = -log10[OH-]
What does pH and pOH add to?
14.0
How are Kw, Ka and Kb linked?
Kw= Ka x Kb
How is pKa linked to pH?
pKa= pH + log10[HA]/[A-]
What is the relationship between Ka and pKa?
The higher the Ka, the lower the pKa
Why are acid base titrations done?
To accurately determine the amount of acid in a solution.
Why can’t a pH meter just be used?
This only tells us the concentration of [H3O+]. So it is okay only if the acid is a strong acid or base.
What is the general method of a titration?
Pipette a known volume of solution A into the conical flask.
Add 2-3 drops of indicator to the conical flask.
Solution B of known concentration (reacts with solution A) is added to the conical flask from the burette until the equivalence point is reached.
What must the pH of the end point of the titration be matched to?
The pKa of the indicator
What is the indicator range?
pKa plus or minus 1
For strong base added to weak acid titration, what is there before the equivalence point?
The solution contains HA and A-
For strong base added to weak acid titration, what is there at the equivalence point?
The solution contains A- (conjugate base)
It is basic
For strong base added to weak acid titration, what is there after the equivalence point?
The solution contains excess OH- (from base)
Very basic
For strong acid added to weak base titration, what is there before the equivalence point?
The solution contains HA and A-
For strong acid added to weak base titration, what is there at the equivalence point?
The solution contains HA (conjugate acid)
It is acid so treat it as a weak acid
For strong acid added to weak base titration, what is there after the equivalence point?
The solution contains excess H3O+ (from base)
Acidic
Treat as a strong acid
