Chapter 8 Review
I.
8.1
A. Properties of acids and bases
Property
Acid (vinegar)
Base (soap)
Taste
Sour
Bitter
Texture
None
slippery
Reaction with
phenolphthalein
colorless
Turns pink/purple
Reaction with litmus
Blue litmus -> red
Red litmus -> blue
Reaction with metals
Some metals release H2
NR
Reaction with CO3
Release CO2 gas
NR
Reaction with NH4Cl
NR
Release NH3 gas
Reaction with fatty acids
NR
Produce soaps
Neutralization
Neutralize base
Neutralize acids
II.
1.
-
Acid-base theory
Arrhenius
Based on ions produced
Acids: produce hydronium ions
Base: produce hydroxide ions
Limitations:
- unable to explain role of H2O molecules
- Failed to explain basic nature of ammonia => why it acted as a base
2. Bronsted
- Based on H protons
- Acids: proton H donor
- Base: accept H proton
- Limitations:
- Amphoteric: substances that can act as both a base and an acid (water)
-
A. Conjugate acid-base pairs
Conjugated acid: forms when a base accepts H protons
Conjugated base: forms when an acid loses H protons
-
B. Acid ionization constant Ka
When acids ionize and dissociate => dynamic equilibrium
-
II.
-
Where the stronger base is, the system will shift to the opposite side since they both
compete for H ions
Strong and weak acids
6 strong acids: HCl, HBr, HI, H2SO4, HNO3, HClO4 (So I Brought No Clean Clothes)
Strong acids ionize complete (1 arrow)
Weak acids partially ionize (2 arrows)
All hydroxides are strong base
Weak bases: NH3, CO3, HCO3
↑ Ka -> ↑ Acids => equilibrium shift to the right => [H] = [HA]
↓ Ka -> ↓ Acids => equilibrium shift to the left => [H] < [HA]
Stronger acid => weaker conj base
Weaker acid => stronger conj base
a. Types of acids
- Binary:
- 2 elements: HBr, HCl
- Oxy:
- H2SO4
- Organic:
- CH3COOH: acetic
b. Base ionization
c.
-
Water as an acid and base
Most common amphiprotic
Autoionization of water is very weak
Kw = 1.0 x 10^-1 at 25C and SATP
d. Relationship between Kw, Ka and Kb
e.
-
pH and pOH scale and sig fig
pH = -log[H]
[H] = 10^-pH
pOH = -log[OH]
[OH] = 10^-pOH
pH + pOH = 14
a. Sig fig
- Those numbers to the right of decimal count as significant figures
- pH = 10.26 => 2 sig fig
III.
-
Calculations involving acidic
Lower pKa -> stronger acid
Stronger pKa -> weaker acid
Since Ka can be very small, it can be converted to pKa => lower pKa => stronger acid
Ka doesn’t have any impacts on sig fig
a. Percent dissociation
IV.
V.
Given weak acid: ↑ dissociation => ↓ acid
Weak polyprotic acids
Examples: H3PO4, H2CO3
Dissociate in many steps
pH is based on 1st step => highest Ka
-
Calculations involving basic
Must include H2O in base equations but none in equilibrium expression if it’s not a
strong base (amine, methyl, etc)
No H2O in the equilibrium equation for strong bases (OH aka hydroxides)
-
Acid base properties of salt
Salt is an ionic compound
-
VI.
-
Cation (+) comes first and then anion (-)
When dissolved in water => break into ions
Reaction of ions of salts with water is called hydrolysis
a. Salts that produce neutral solutions
- Cations: strong bases
- Anions: strong acids
=> no effect on water since strong - strong => neutral
b. Salts that produce basic solutions
- Cations: neutral
- Anion: conjugate of a weak acid => strong base
=> produce basic solutions
c. Salts that produce acidic solutions
- Cation: conjugate acid of a weak base => strong acid
- Anion: neutral
=> acidic
- Metal ions from group IA and IIA do not hydrolyze
d. Salts in which both hydrolyze
- Anything strong will hydrolyze water
- Anything weak doesn’t hydrolyze water
- if :
- Ka > Kb => acidic
- Kb > Ka => basic
- Ka = Kb = neutral