Type

Examples

Approximate
Formulas

Strong
Acid

HCl,
HNO_{3}, H_{2}SO_{4} (first proton), HClO_{4}

[H^{+}]
= C_{SA}, (if C_{SA} > 10^{6})
pH = log [H^{+}]

Strong
Base

NaOH,
KOH, Ba(OH)_{2}

[OH^{}]
= C_{SB}, (if C_{SB} > 10^{6})
[H^{+}] = K_{w}/[OH^{}]

Weak
Acid

Acids
with a K_{a}, e.g. CH_{3}COOH, or salts of weak bases, e.g.
NH_{4}Cl.


Weak
Base

Bases
with a K_{b} (mostly amines, e.g. NH_{3}), or salts of weak
acids, e.g. CH_{3}COO^{}Na^{+}.

_{}

Buffer

Mixtures
of weak acids and their conjugate bases, e.g. CH_{3}COOH mixed with
CH_{3}COO^{}Na^{+}


Amphiprotic
(polyprotic)

NaHCO_{3},
KHPhthalate


Some Extensions to the formulas above:
The quadratic equation may need to be solved. For ax^{2}+bx+c = 0,
For very dilute strong acids or bases, e.g. C_{HCl} = 10^{8} M HCl, charge balance gives us
[H^{+}] = [Cl^{}] + [OH^{}], from which we get . Rearrange into standard quadratic equation form and solve for [H^{+}].
For weak acids or bases, if successive approximation does not converge, convert the equation into the quadratic equation form and solve for [H^{+}] or [OH^{}]
Dilute Buffers may require this extended equation:
The Full Amphiprotic Equation is: