Chpt 16: Acid Base Chemical Equilibria Flashcards
How should you find the pH if you’re mixing 2 different weak acids, where one acid is way weaker than the other?
Do the ICE table for the stronger of the two weak acids.
the weaker acid’s [H+] won’t contribute much to the overall pH
Why does conjugate resonance impact the strength of carboxylic acids?
if the conjugate (which an an anion) is stable 2o to its resonance, it is not likely to reclaim H+ to become an acid
what does pH + pOH equal?
14
One of the types of weak bases is neutral structures with unpaired e-. What are the two kinds of neutral structures with unpaired e-?
NH3 and amines
what is the expression for “Ka” ?
[H+][A-]/[HA]
what does Kw equal at room temperature?
1.0E-14
what does [H+][OH-] equal?
1.0E-14
how does bond strength generally impact the strength of an acid/base
stronger bond, weaker acid/base
True or false: when comparing the strength of weak bases, the more negative the base’s charge, the more attractive it is to H+
True; More negative, more ability to accept H+
exp. HCO3^- is a weaker base than CO3^2-
what are salts?
ionic compounds that make ions in solution
what is an amine?
type of weak bases:
characterized as a neutral substance with a nitrogen that has an unbound electron pair for accepting H+
how does conjugate stability generally impact the strength of an acid or base?
the more stable the conjugate, the more stronger the acid/base?
How do oxyacids’ strength trend as more terminal oxygens are added?
more terminal oxygens, stronger acid (because polarity goes up as oxygens are added)
true or false: if an acid/base is a Lewis acid/base, it must also be a BL acid/based and a Arrhenius acid/base
false. (because Lewis acids/bases’ definition does not depend upon H+ involvement like the BL and Arrhenius definitions do)
Lewis is the most general of all the definitions
true or false: in the case of oxyacids, the more terminal oxygens around central atom, the stronger the acid?
true
what would happen if you forgot the - sign while trying to go from pH to [H+] using your elementary school calculator
it would give you the wrong answer
what is an oxyacid?
A molecule in which a central atom is surrounded by terminal atoms (sometimes terminal oxygens), including an OH- group or groups
how does atomic radii generally impact bond strength?
bigger radii, weaker bond
If you’re mixing a weak acid and a weak base, how can you tell whether the pH will be acidic or basic?
The component with the larger Keq will be the one that determines the pH
Exp.if Ka is bigger than kb, the solution will be acidic
what is the expression for “Kw” (in terms of ka and kb)?
ka * kb = kw
what does the “Kw” k constant represent?
the autoionization of water
how are Lewis acids defined?
as electron pair acceptors
what are binary acids?
acids that only have two kinds of atoms in them
how are Lewis bases defined?
as electron donors
true or false: the stronger the acid, the weaker the base
true
what does the “Ka” k constant represent?
ratio of ions to acid molecules
when do you have to bother with ICE tables: with strong acids/bases or weak acids/bases?
waek
how do you go from [H+] to pH?
take the -log of [H+]
what are the two types of weak bases?
neutral structures (that have unpaired e- for accepting H+)
charged structures (that are conjugates of weak acids)
true or false: if an acid/base is a BL acid/based or a Arrhenius acid/base, it must also be a Lewis acid/base
true
in a chemical reaction, how can you tell which component acts as a Lewis BASE
it will give its unpaired electrons to something else
exp. if Fe(ClO4)3 + 6H2O makes Fe(H2O)6 + 3ClO4^1, H2O gave its unpaired electrons to Fe^3+, and is thus acting as a base
how does bond strength trend on the periodic table?
strength goes up as you go up the periodic table
in a chemical reaction, how can you tell which component acts as a Lewis acid
it will accept/receive something else’s electron pair
exp. if Fe(ClO4)3 + 6H2O makes Fe(H2O)6 + 3ClO4^1, the Fe receives the unpaired electrons that H2O had, and is thus acting as an acid
in ka or kb problems, when can you ignore the x in the denominator?
when the acid or base concentration decreases by less than 5% in order to achieve equilibrium
and/or
when your final acid or base concentration is 5% or less of the original concentration
When comparing weak acid or base strength, what can you consider in addition to polarity, bond strength, and stability of the acid’s/base’s conjugate?
the ka or kb values involved
what does a large ka mean?
large ionization; strong acid
how does binary acid strength trend as you go across the periodic table?
acid gets stronger as you go to the right (bc polarity increases)
what is the expression for “Kw” (in terms of H+ and OH- concentrations)?
kw = [H+][OH-]
how do you go from pH to [H+] using your elementary school calculator?
2nd, LOG, -, [pH]
you have to remember the - sign!!!
true or false: in the case of oxyacids, the more electronegative the central atom, the stronger the acid?
true
How do oxyacids’ strength trend as the OXIDATION NUMBER of their central atom increases?
higher the oxi number, stronger the acid
How do oxyacids’ strength trend as the electronegativity of their central atom increases?
acid gets stronger as electronegativity of the central atom goes up
How should you find the pH if you’re mixing 2 different weak acids, where both acids are equally weak?
Do the ICE table for both, find the [H+] for both, add the two [H+] values together, and use that to calculate the pH
how does binary acid strength trend as you go up the periodic table?
acid gets stronger as you go down the table (bc bond strength gets weaker as radius increases)
how does polarity generally impact the strength of an acid or base?
bigger dipole, strong acid/base
