Exam 4 Flashcards
(22 cards)
H-H equation (buffer pH calc)
pH = pKa + log ( [base] / [acid] )
or [A-] / [HA]
Entropy
Measure of disorder/randomness
Factors that affect acid strength: 3
- Polarity of H-X
- Size of anions X-
- Stability of conj. base X-
polarity of H-X bond that affects acid strength…
- to release H+, bond must be polarized
- more polar=more willing to donate
- stronger polarity=stronger acid
strength of H-X bond that affects acid strength
- weaker H-X bond breaks easily, increasing acidity
- Larger X- = weaker bond = stronger acid
- when going DOWN a group in P. Table, bond strength down … acidity up
electronegativity that affects oxoacids (HNO3, H2SO4 …)
higher EN = stronger acid
of oxygen atoms in oxyacid
MORE oxygen = STRONGER acid
purpose of a buffer
resist change to pH, maintains it stable
how buffers work?
weak acid + conj. base = buffer
this effect suppresses dissociation and allows soln to neutralize any added bases or acids.
common ion effect
titration curve: EQ point
where moles of acid = moles of base
titration curve: midpoint
for weak acids…
[acids]=[base] AND pH = pKa
how to find pKa:
half of the equivalence point
what creates a buffer?
- weak acid + salt
- weak base + salt
what is a buffering capacity?
how much acid or base the buffer can neutralize before pH changes significantly
(higher conc. = higher capacity)
when adding acid or base to a buffer, before doing the H-H eq… you must
adjust concentrations
add base … subtract from acid
add acid … subtract from base
midpoint is where…
acid = base and
pH = pKa
meaning of Ksp:
constant @ given temp
- higher = more soluble salt
- lower = salt is less soluble (ppt easier)
🔺H = -
🔺S = +
ALWAYS spontaneous
🔺H = +
🔺S = -
NEVER spontaneous
🔺H = +
🔺S = +
ONLY @ HIGH TEMP
🔺H = -
🔺S = -
ONLY @ LOW TEMP
