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 Pure H2O at 25 °C 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 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. Calculations: [H+] > 1.0 x 10-7M [H+] = 6.0 x 10 -10M 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 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