LO 59 - 65 Flashcards
What is a titration?
Acid or base of unknown concentration is neutralized with an acid/base of known concentration
What is the equivalence point of a titration?
Point in which the number of mols of base is stoichiometrically equal to the number of mols of acid
The equivalence point of a strong acid + strong base titration is always pH = ____
7.0
[H30+] before the equivalence point of a SA + SB titration is calculated by . . .
Since [H30+] is in excess before the eq.
[H30+] = (mol H30 initial - mol OH added)/total volume
[OH-] after the equivalence point of a SA + SB titration is calculated by . . .
Since [OH-] is in excess after the eq.
[OH-] = (mol OH added - mol H3O initial)/total volume
What are the 5 steps to titrating a weak acid of unknown concentration with a strong base?
- Find the volume strong base needed to reach EQ using V1M1=V2M2
- Find the initial H3O+ concentration from initial pH
- Set up a Δmols table where the desired amount of OH- reacts with the weak acid to form H2O and the conjugate base (buffer)
- Use HH equation to find buffer pH from additions
- At equilibrium only conjugate base is left so calculate pH using an equilibrium problem as it ionizes with H2O
When pH=pKa of a buffer solution as more strong base is added to a weak acid, you’re . . .
halfway to the equivalence point
A = log(X) can be canceled out by . . .
A = log(X) –> 10^A = X
When titrating a weak acid with a strong base the eq. point will have a slightly ________ pH
basic
When titrating a weak base with a strong acid the eq. point will have a slightly ________ pH
acidic
When titrating a weak base with a strong acid the pKa in the HH equation corresponds to . . .
the conjugate acid of the weak base that is being titrated
When titrating polyprotic acids with sufficiently different Ka1 and Ka2, the pH curve will have . . .
2 equivalence points
pH indicators are commonly . . .
weak organic acids
With an indicator, we rely on the point when there is a change in color known as the _________ to determine the eq. point
endpoint
The _____________ is the equilibrium expression of a chemical equation representing the dissolution of a slight to moderately soluble ionic compound
solubility product constant (Ksp)
__________ is the solubility of a compound in units of mols per L
molar solubility
The relationship between Ksp and molar solubility depends on . . .
the stoichiometry of the dissociation reaction
What are Ksp and molar solubility comparable to in calculation?
A RICE table in which the rxn is the dissociation reaction, Ksp is the K value, and molar solubility is the x value
What is the result of the common ion effect?
Generally, the solubility of an ionic compound is LOWER in a solution containing a common ion than it would be in H2O
The solubility of an ionic compound with a strong or weak basic anion __________ with increasing acidity (lower pH)
Increases
Given an ionic compound with a strong or weak basic anion in a solution with a high pH, what happens to the dissociation reaction?
If the pH is high there is more OH - in solution (product), shifting the dissociation reaction left, lowering solubility
Given an ionic compound with a strong or weak basic anion in a solution with a low pH, what happens to the dissociation reaction?
If the pH is low there is more H3O+ in solution (reactant with the OH- produced), shifting the dissociation reaction right, increasing solubility
When calculating the molar solubility of an ionic compound in a common ion solution, what do you need to remember about the RICE table?
That the produced ion will NOT be 0 initially but rather be equal to the concentration of the same ion already in solution
Q < Ksp
solution is unsaturated and more solid ionic compound can dissolve
Q = Ksp
solution is saturated and is holding the EQ amount of dissolved ion. added solid will not dissolve
Q > Ksp
the solution is supersaturated and under most circumstances will precipitate excess solid
_____________ is the process in which the addition of a reagent will form a precipitate with one select cation of those in solution
selective precipitation
