Acid-Base Equilibrium

strong acids

HCl, HBr, HI, HNO_3, HClO_4, H₂SO₄

strong bases:

XOH, Ba(OH)₂, Sr(OH)₂; X is any alkali metal (first column of Periodic Table)

if acid or base is strong…

there will be 100% yield of [H⁺] or [OH^-]

if acid or base is weak…

must be told percent yield or apply equilibrium

acidic

pH < 7

basic

pH > 7

sig fig rule when connecting Molarity with pH or pOH..

the number of sig figs, in Molarity correspond to the number of decimal places for pOH or pH

all acid-base reactions are…

double replacement and yield water

strong acid + strong base

pH = 7

weak acid + strong base

pH > 7

strong acid + weak base

pH < 7

Bronsted-lowry acid

proton donor in H₂O

Bronsted-lowry base

proton acceptor in H₂O

amphiprotic

any species capable of donating as well as accepting H⁺

K_A expression:

products/reactants (AQ ONLY)

buffered solution

1. weak acid +conjugate base

2. weak base + conjugate acid

spectator ions

ARE IGNORED; all sodium (Na), nitrate (NO₃^-, ammonium (NH₄⁺), & potassium (K) containing compounds are soluble in water

alternate method for buffer calculations

“Henderson-Hasselbalch equation”; A = base HA = acid

what makes a buffer optimal?

1. select ingredients where the pH of buffer is closest to pK_A

2. two buffer ingredients are more concentrated

endpoint

the instant where indicator changes color to signal a completed titration; ideally, endpoint and equivalence point are to match

phenolphthalein

ph = 7

methyl red

ph < 7

thymol blue

ph > 7

weak acid/strong base titration curve

initial weak acid present; pH was recorded and it will be able to calculate [H₃O⁺] at equilibrium; if concentration of weak acid is known you can calculate K_A

percent dissociation

[H₃O⁺] / [weak acid]

buffer region

the section at which the pH is resistant to cane.

half-equivalence point

pH = pK_A

equivalence point

data point where acid/base neutralization occurs according to M_AV_A = M_BV_B; this solves M_A [weak acid]

in the beginning of buffer region

pH < pK_A, so [HA] > [A^-]

past half-equivalence point

ph > pK_A , so [HA] < [A^-]