Acids and Bases
Acids
• Tart or Sour taste
• Electrolytes
• React with bases to form H2O
& a salt
• Produces H+ (hydrogen ions)
when dissolved in H2O
• General form - HX
Bases
•
•
•
•
Bitter Taste
Feel slippery
Electrolytes
React with acids to form H2O
& a salt
–
• Produces OH (hydroxide ions)
when dissolved in H2O
Naming Acids
• Identify name of anion
• Anion ends in “-ide”, acid name begins
with “hydro” – (Cl - chloride)
• Stem of anion ends in “-ic”, followed by
“acid”
– HCl  Hydrochloric Acid
– H2S  Hydrosulfuric Acid
Naming Acids cont.
• Anion ends in “-ate” – (SO4 - sulfate)
• Stem of the anion ends in “-ic”,
followed by “acid”
– H2SO4  Sulfuric Acid
– HNO3  Nitric Acid
Naming Acids cont.
• Anion ends in “-ite” – (SO3 - sulfite)
• Stem of the anion ends in “-ous”, followed
by “acid”
– H2SO3  Sulfurous Acid
– HNO2  Nitrous Acid
Write the Formula
•
•
•
•
Chloric Acid
Hydrobromic Acid
Phosphorous Acid
Carbonic Acid
•
•
•
•
HClO3
HBr
H3PO3
H2CO3
Naming Bases
• Ionic compounds
• Name as an ionic compound
– Name of cation followed by anion
• NaOH  Sodium Hydroxide
• Ca(OH)2  Calcium Hydroxide
Water
• Water molecules are highly polar
– Continuous motion
• Occasionally, collisions between H2O
molecules are energetic enough to transfer a
H+ -- Self-ionization
H2O + H2O  H3O+ + OH• H3O+ – Hydronium Ion
Water (cont.)
• Self-ionization reaction
– H2O(l)  H+(aq) + OH-(aq)
• Pure H2O at 25 °C
– [H+] = [OH-] = 1.0 x 10-7M
• Ion-product constant for water (Kw)
– Kw = [H+] x [OH-] = 1.0 x 10-14M2
Acidity
+
(H )/Basicity
(OH )
• Acidic solutions – [H+] is greater than [OH-]
– [H+] is greater than 1.0 x 10-7M
– [OH-] is less than 1.0 x 10-7M
• Basic solutions – [H+] is less than [OH-]
– [H+] is less than 1.0 x 10-7M
– [OH-] is greater than 1.0 x 10-7M
Acidic or Basic Solution?
Not all solutions are neutral!!! [H+] = [OH-]
• Acidic soln – release H+
• HCl(aq)  H+(aq) + Cl-(aq)
• Basic Soln – release OH• NaOH(aq)  Na+(aq) + OH-(aq)
• [H+] > 1.0 x 10-7M
• [H+] > [OH-]
• [H+] < 1.0 x 10-7M
• [H+] < [OH-]
Classify – Acidic, Basic, Neutral
• [H+] = 1.0 x 10-9M
• [OH-] = 2.0 x 10-5M
• If [H+] = 1.0 x 10-4M,
is the solution acidic,
basic or neutral?
• What is the [OH-]?
• Basic
• Basic
• Acidic
• Kw = [H+] x [OH-]
• [OH-] = Kw / [H+]
• [OH-] = 1.0 x 10-14M2 / 1.0 x
10-4M
• = 1.0 x 10-10M
pH Scale
• pH – scale used to express [H+]
• Ranges from 0 – 14
– pH=0 Strongly acidic
– pH=14 Strongly basic
• pH = - log [H+]
Ex. Neutral Solution
[H+] = 1.0 x 10-7M
pH = - log (1.0 x 10-7M) = 7
pH cont.
• [H+] > 1.0 x 10-7M
– then pH < 7 (acidic)
• [H+] < 1.0 x 10-7M
– then pH > 7 (basic)
• Recall
[H+][OH-]= 1.0 x 10-14M
• Calculations:
• [H+] = 6.0 x 10 -10M
Acidic or Basic?
pH = ?
[OH-] = ?
pOH Scale & calculations
• pOH– scale used to express [OH-]
• pOH = - log [OH-]
• pH + pOH = 14
• If pH = 6.5, calculate pOH & [OH-].
• pOH = 14 – 6.5 = 7.5
• [OH-]= 10-pOH = 10-7.5 = 3.1 x 10-8M
Measuring pH
• Why – swimming pools, soil, medical (diabetes)
• How
– 1. Acid – Base indicators – change color at a
specific pH
• Ex. phenothalein, thymol blue …
– (Pg. 590 Figure 20.8)
– 2. Litmus paper
– 3. pH meters – make rapid & accurate
measurements
Assignment
Name each acid or base:
• a. HF
• e. HClO3
b. KOH
f. Al(OH)3
c. HNO3
g. H3PO3
d. H2SO4
h. Fe(OH)3
Write the formula for each acid or base:
•
•
•
•
a. barium hydroxide
c. chromic acid
e. rubidium hydroxide
g. chlorous acid
b. hydroselenic acid
d. hydrobromic acid
f. iron(II) hydroxide
h. sulfurous acid
Identify each property as applying to an acid,
a base or both.
• a. bitter taste
• c. electrolyte
b. indicator color change
d. sour taste
Assignment Continued
• Pg. 658 – 35, 41-43
• pH Worksheet