Acids and Bases

Acids Tart or Sour taste Electrolytes React with bases to form H 2 O & a salt Produces H + (hydrogen ions) when dissolved in H 2 O General form - HX

Bases Bitter Taste Feel slippery Electrolytes React with acids to form H 2 O & a salt Produces OH – (hydroxide ions) when dissolved in H 2 O

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 –H 2 S  Hydrosulfuric Acid

Naming Acids cont. Anion ends in “-ate” – (SO 4 - sulfate) Stem of the anion ends in “-ic”, followed by “acid” –H 2 SO 4  Sulfuric Acid –HNO 3  Nitric Acid

Naming Acids cont. Anion ends in “-ite” – (SO 3 - sulfite) Stem of the anion ends in “-ous”, followed by “acid” –H 2 SO 3  Sulfurous Acid –HNO 2  Nitrous Acid

Write the Formula Chloric Acid Hydrobromic Acid Phosphorous Acid Carbonic Acid HClO 3 HBr H 3 PO 3 H 2 CO 3

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 H 2 O molecules are energetic enough to transfer a H + -- Self-ionization H 2 O + H 2 O  H 3 O + + OH - H 3 O + – Hydronium Ion

Water (cont.) Self-ionization reaction –H 2 O (l)  H + (aq) + OH - (aq) Pure H 2 O at 25 °C –[H + ] = [OH - ] = 1.0 x M Ion-product constant for water (K w ) –K w = [H + ] x [OH - ] = 1.0 x M 2

Acidity (H + )/Basicity (OH - ) Acidic solutions – [H + ] is greater than [OH - ] –[H + ] is greater than 1.0 x M –[OH - ] is less than 1.0 x M Basic solutions – [H + ] is less than [OH - ] –[H + ] is less than 1.0 x M –[OH - ] is greater than 1.0 x M

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 M [H + ] > [OH - ] Basic Soln – release OH - NaOH (aq)  Na + (aq) + OH - (aq) [H + ] < 1.0 x M [H + ] < [OH - ]

Classify – Acidic, Basic, Neutral [H + ] = 1.0 x M [OH - ] = 2.0 x M If [H + ] = 1.0 x M, is the solution acidic, basic or neutral? What is the [OH - ]? Basic Acidic K w = [H + ] x [OH - ] [OH - ] = K w / [H + ] [OH - ] = 1.0 x M 2 / 1.0 x M = 1.0 x M

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 M pH = - log (1.0 x M) = 7

pH cont. [H + ] > 1.0 x M –then pH < 7 (acidic) [H + ] < 1.0 x M –then pH > 7 (basic) Recall [H + ][OH - ]= 1.0 x M Calculations: [H + ] = 6.0 x M 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 = = 3.1 x M

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. HFb. KOHc. HNO 3 d. H 2 SO 4 e. HClO 3 f. Al(OH) 3 g. H 3 PO 3 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 tasteb. indicator color change c. electrolyted. sour taste

Assignment Continued Pg. 658 – 35, pH Worksheet