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)

• [H+] > 1.0 x 10-7M• [H+] > [OH-]

• Basic Soln – release OH-

• NaOH(aq) Na+

(aq) + OH-(aq)

• [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

AssignmentName each acid or base:• a. HF b. KOH c. HNO3 d. H2SO4

• e. HClO3 f. Al(OH)3 g. H3PO3 h. Fe(OH)3

Write the formula for each acid or base:• a. barium hydroxide b. hydroselenic acid • c. chromic acid d. hydrobromic acid • e. rubidium hydroxide f. iron(II) hydroxide • g. chlorous acid h. sulfurous acid

Identify each property as applying to an acid, a base or both.• a. bitter taste b. indicator color change• c. electrolyte d. sour taste

Assignment Continued

• Pg. 658 – 35, 41-43• pH Worksheet