Acids and Bases AcidBase Theories Arrhenius Theory Acid

Acids and Bases

Acid/Base Theories Arrhenius Theory: Acid: substance that releases H+ ions HCl H+ + Cl- Base: substance that releases OHions Na. OH Na+ + OH-

Acid/Base Theories Bronsted-Lowry Theory: Acid: Any substance that donates a proton (H+) Base: Any chemical that accepts a proton

Bronted-Lowry (cont) Ex: HCl + H 2 O Acid HCl Base H 2 O H 3 O+ + Cl- Each acid becomes the Conjugate Base: gains the H+ in the reverse reaction Cl. Each base becomes the Conjugate Acid: releases the H+ in the reverse reaction H 3 O+

Acid/Base Theories Lewis: Acid: acceptor of e- pair (binds to epair) Base: donor of an e- pair (available e-)

Lewis Theory (cont. ) NH 3(aq) + H 2 O(l) NH 4+(aq) + OH-

Naming Acids Binary Acids: two elements “hydro” + element stem + “ic” acid Ex: HCl hydrochloric acid HF hydrofluoric acid HI hydroiodic acid

Naming Acids Ternary Acids: more than two elements Most common: stem + “ic” One less oxygen: stem + “ous” Two less oxygens: “hypo” + stem + “ous” One more oxygen: “per” + stem + “ic”

Ternary Acid Examples H 2 SO 4 – Sulfuric p H 2 SO 3 – Sulfurous p HCl. O 3 – Chloric p HCl. O 2 – Chlorous p HCl. O – Hypochlorous p HCl. O 4 – Perchloric p H 3 PO 4 – Phosphoric p H 2 CO 3 – Carbonic p

Naming Bases Ionic Compound with a hydroxide Ex: Na. OH – Sodium Hydroxide KOH – Potassium Hydroxide

Acid OR Base? If a compound contains oxygen (H-OX), the electronegativity of the element (X) determines whether it will be an acid or a base p If “X” has a high electronegativity, the “H” dissociates acid p If “X” has a low electronegativity, the “OH” dissociates base p

Acid/Base Reaction Neutralization Reaction: Acid + Base Water + Salt Ex: HA + BOH H+ + A- + B+ + OH- HOH + BA

Neutralization Reactions p HCl + Na. OH Na. Cl + HOH

Neutralization Reactions p H 2 SO 4 + 2 NH 4 OH (NH 4)2 SO 4 + 2 HOH

Neutralization Reactions 2 Na. OH + H 2 CO 3 2 HOH + Na 2 CO 3

Other Characteristics Acids: Taste sour Turn litmus paper red Bases: Taste Bitter Feel slippery – dissolving your skin Turn litmus paper blue

Measuring p. H = per Hydrion or the concentration of the Hydronium ion H 2 O + H + = H 3 O+ The negative (–) logarithm of the concentration = p. H If the [H 3 O+] = 1 x 10 -3 then the p. H = 3 The lower the concentration, the higher the p. H. PAGE 611, # 19

Finding the concentration from the p. H. p 10^(-p. H) p p p. H = 4. 30 n Concentration = 10^(-4. 30) = 5. 01 x 10 -5

Measuring p. OH = per hydroxide The –log [OH-] For any solution the p. H + p. OH = 14. 0 Therefore, the higher the p. H, the lower the p. OH Page 612, # 20

p. H/p. OH relationship

Strength of Acids and Bases p Strong Acid/Base: H+/OH- ion dissociates completely – more H+/OH- = stronger change Ex: HCl (monoprotic) H 2 SO 4 (polyprotic) Na. OH KOH

Strength of Acids and Bases Weak Acid/Base: H+/OH- ion does not dissociate completely p Page 603 p n less H+/OH- = weaker change Ex: CH 3 COOH NH 3

Strength vs. Concentration Strong vs. Weak Concentrated vs. Dilute A weak acid can be very harmful if it is concentrated. A strong acid could be less harmful if it is dilute. What does p. H/p. OH indicate?

Testing Acids and Bases p Litmus Paper

Testing Acids and Bases p. H Paper

Testing Acids and Bases p Indicator Solutions

Titrations Using a solution of known concentration to determine the concentration of an unknown solution. Uses an indicator chemical to indicate the change in p. H.

Titration Animation