Acid-Base Chemistry (Ch 6 and 9)

How do you identify acidic, basic, and neutral solutions?

Determine [H⁺] or [OH^-] → find pH

What are strong acids? 6

Dissociate completely

HCl, HBr, HI, HNO₃, HClO₄, H₂SO₄

How do you determine the dominant form of an acid/base at given pH?

Henderson-Hasselbalch equation

pH = pKa + log ([A^-]/[HA])

If pH > pKa → more conjugate base

If pH < pKa → more undissociated acid

How do you determine pH of an acidic solution?

1. Write out the chemical equation

2. Identify the acid

3. Make ICE table

4. Ka = x²/(F-x) where x is the change and F is the initial concentration of acid (if x is more than 100 times smaller than F, disregard)

How do you determine pH of a basic solution?

1. Write out the chemical equation

2. Identify the acid

3. Make ICE table

4. Ka = x²/(F-x) where x is the change and F is the initial concentration of acid (if x is more than 100 times smaller than F, disregard)

5. Use (Ka)(Kb) = Kw

6. Use Kb = x²/(F-x) and solve for x (if x is more than 100 times smaller than F, disregard)

How are Ka, Kb, and Kw related?

(Ka)(Kb) = Kw = 1.00 × 10^-14

pKa + pKb = pKw = 14.00

How do you determine percentage of protonated/unprotonated form of a given acid/base?

x/F (100)

How do you chose an acid/base for a given buffer?

You want one that has a pKa within ± 1 of the pH

What are characteristics of a buffer solution?

Contains significant amounts of both acid and base

How is pH of a buffer determined?

Use HH

pH = pKa + log [B]/[HB⁺] for base

pH = pKa + log [A^-]/[HA] for acid

How do you make a buffer?

Basic: mix weak base with salt of conjugate acid or titrate weak base with strong acid

Acidic: mix weak acid with salt of conjugate base or titrate weak acid with strong base

How do you find pH after adding a base or acid to a buffer?

1. Find concentrations of A^-, HA, B, HB⁺ depending on what you need

2. Add in the concentration acid/base you are using (use ICE table)

3. Use HH