Acids, Bases, and Salts

pH is less than 7

It is acidic

pH is greater than 7

It is basic

Autoionization of Water

The concentrations of [H3O+] and [OH-] are equal in water (1 × 10^-7 M) at 25 degrees.

What does ka > 1 mean?

The molecule is a strong acid and completely ionizes in water.

What does ka < 1 mean?

The molecule is a weak acid and do not donate much of their hydrogens to water.

What are the six strong acids?

HCl, HBr, HI, HNO3, HCLO4, and H2SO4.

What are weak acids?

CH3COOH, H2CO3, HCOOH

What is Kw?

The dissociation constant of water: [H3O+] [OH-]=1.00 × 10^-14.

Strong Bases

KOH, NaOH, Ca(OH)2

Strong Acids

HI, HCl, HBr, HNO3, H2SO4, HClO4. Their concentrations will also be the same as [H3O+].

How do you solve for pH

-log(H3O+)

How do you find the pOH?

-log(OH-)

PKa interpretation

A lower pka indicates a stronger acid, as a higher ka indicates a stronger acid.

PKb Interpretation

A lower pkb indicates a stronger base, as a higher kb value indicates a strong base.

How do you find Pka?

-log(Ka)

How do you find PKb?

-log(Kb)

How do you find [H3O+]?

10^pH

Solving for mixtures of weak acids

See which one is the weakest and completely discard. Then use the stronger one to solve for [H3O+] and use for -log(H3O+) for pH.

How do you find pOH?

-log(OH-)

What happens to the pH of a buffer solution when an acid or base is added?

The pH of the buffer solution should remain relatively the same or change slightly as long as there are significant amounts of each of the buffer components (conjugate base or acid).

Henderson-Hasselbalch Equation

pH=PKa + log [base]/[acid]