Aqueous equilibria Flashcards
Common Ion Effect
Shift in the position of equilibrium when you add something already involved in that equilibrium
Chataliers principle
When something in equilibrium is changed, something else will try to counterbalance it. (seesaw)
Buffers
Solutions that RESIST changes in pH when limited amounts of acid or base are added (maintains pH)
WHat does a good buffer contain
conjugate acid and base in similar amounts
Source of protons in a buffer is to? where does it get added?
Neutralize incoming bases
OH- into the reactants side
Sink of protons in a buffer is to? Where does it get added?
neutralize incoming acids
H30 into the products side
Henderson hasselbalch equation
pH = pKa +log([base(A) ]/[acid HA])
What does Henderson hasselbalch equation highlight
the pH of a buffer solution has a value close to the pKa of the weak acid
Buffer capacity: the ______ ______ of acid or base which the buffer can handle without significant _______ in pH
Molar amount
Changes
For buffers: large shifts in the acid or base concentration =
small changes in pH
Step 1 of Two Step approach for buffers:
Step 1: Find major species that remain after any strong acids or bases act (assume completion)
Step 2 of Two Step approach for buffers:
Step 2: Determine the concentration of minor species that the major species generate.
If have both acid and conjugate base in step 2 –> ______ –> H-H
buffer
If only weak acid/base in step 2,
Acid/base dissociation –> ice table
If have either H30+ or OH- directly remaining in step 2 from step 1,
Done
Titration is a procedure for
determining the concentration of a solution by reacting it with another substance with a known concentration
Titrations involving only strong acids or bases are
straightforward
Titrations involving weak acids or bases are _________ by the ___________ of salts
complicated
dissociation
Equivalence point
The point at which stoichiometrically equivalent quantities of acid and base have been mixed together
At the equivalence point, what is happening?
Moles of base = moles of acid
(perfect neutralization)
Which one has a higher equivalence point pH?
Weak acid-strong base titration
Strong acid-strong base titration
Weak acid-strong base titration
pH in WEAK ACID/STRONG BASE TITRATIONS: “A” on graph (before addition of NaOH)
Ka = [H30+][A-] / [HA]
-log[H30] to find pH
pH at “B”: before the equivalence point (Buffer region) (addition of something u use hen law)
pH = pKa + log [A-]/[HA]
NOTE!! when [HA]=[A-], pH = pKa
finding pH at “C”: at the equivalence point
All of the HA has been converted to A, solution is basic, so use ice table and find KB
finding pH at “D”: after equivalence point
there will be excess [OH] so u just convert that to pH
Acid-base indicator
something that changes colour in specific pH range
Why does acid-base indicator change colour depending on pH
They are weak acids and have different colours in their acid and conjugate base forms
A titration graph going UP, the signs are A, B, C, and D. How to determine each?
A: weak ACID equilibrium
B: Buffer
C: equilibrium point (BASIC)
D: Leftover strong BASE
A titration graph going DOWN, the signs are A’, B’, C’, and D’. How to determine each?
A’: weak BASE equilibrium
B’: Buffer
C’: Equilibrium point (ACIDIC)
D’: Leftover Strong ACID
Solubility is
The amount of solute that dissolves in a given amount of solvent (mol/L)
Chemical equation representing solubility
Mm Xx (s) <–> mMⁿ⁺ (aq) + xXʸ⁻ (aq)
Solubility product is represented as Ksp, whats the formula?
Ksp = [Mⁿ⁺]ᵐ [Xʸ⁻]ˣ
Solubility product, Ksp is a measure of
how much of an ionic compound has dissolved at equilibrium
Precipitation of ionic compounds chemical equation
Its similar to solubility chemical equation just diff values:
AB (s) <—-> A+ (aq) + B- (aq)
Qsp’s concentration formula
TIME!!!
Qsp = [A+]ₜ [B-]ₜ
Ksp’s uses _____ instead of t
eq
In solubility equilibriums, you can tell the shift direction if something is added by
common ion: shift opposite of where ion is (solubility decrease)
substance that reacts with one of the ions: Shift towards the side without that ion (solubility increase)
practical buffer range
pKa +- 1
What species are in the buffer region of a weak acid–strong base titration?
comparable amounts of weak acid and its conjugate base
What species in the buffer region of a weak base–strong acid titration?
Predominant amounts of weak base and the conjugate acid
for solving, strong base you
make one ice table and get poh out of that concentration
for solving, weak base you
make one ice able and get that concentration, then u use that concentration and make another ice table to find the concentration for H30 or oH.
DEPENDS IF THERES OH LEFT BRUHHH
