15. Acid-base equilibria

Buffers

buffer: solution that resists change in pH

in human body:

e.g. stomach, sweat, blood, saliva

used to protect you from hurting yourself

making a buffer

weak acid and conjugate

weak base and conjugate

do not use strong acid/base (not reversible)

buffer contains both acid and base; reacts with one and then shifts the other way

buffer capacity: amount of acid/base a buffer can absorb before it breaks

capacity measured in concentration (M)

higher molarity → higher capacity

symbols

strong acid: H⁺ or H₃O⁺

strong base: OH⁻

weak acid: HA

weak base: B

e.g.

strong acid + weak base:

⁠

weak acid + strong base:

⁠

example buffer:

⁠

mix weak acid (e.g. vinegar) with conjugate base (usually salt/solid)

⁠

Na is spectator ion

calculate pH using the concentrations of the acid and base

Henderson-Hasselbalch equation: used to calculate pH of buffers

⁠

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