Homework 3-8 Acid/Base Reactions

Review of H and the Proton Hydrogen, the simplest element, consists of a ___________ and an ____________. If you remove the electron from an H atom, only the proton remains. Our symbol for a proton is: H+

HCl + H2O  Cl– + H3O+ B. Definitions acid conjugate base base Brønsted-Lowry Acids are proton (H+) donors. Bases are proton (H+) acceptors. HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

Example Reactions Which water is the acid and which is the base? Water can act as either an acid or a base (amphoteric)! Which is the acid and which is the base?

Properties of Acids and Bases Taste: Acids sour (vinegar, OJ, wine, aspirin) Bases bitter (coffee, cigarettes, tonic water, baking soda, antacids, soap) Feel: Acids sting Bases slippery

Properties continued Acids always react with active metals. Bases generally do not react with metals. HCl nitric

Properties continued Solutions of both acids and bases are excellent conductors of electricity (ions are free to move!). Link to acid dissociation video

Indicators Indicators are chemicals that turn different colors in acids or bases (different pHs). AciD in litmus = RED, base = bLUE Acid in phenolphthalein = colorless Base in phenolphthalein = pink

Choices for ?’s : A) Acid B) Base C) Both 1) Turns litmus red Ans: A 2) Turns phenolpthlein pink Ans: B 3) Tastes bitter

Choices for ?’s : A) Acid B) Base C) Both 4) Feels slippery Ans: B 5) Solution conducts electricity Ans: C 6) Always Reacts with active metals Ans: A

Be able to recognize these as Acids or Bases in a chemical rxn Acids: HCl = Hydrochloric acid HNO3 = Nitric acid CH3COOH = Acetic acid (or HC2H3O2) H2O = water Bases: NH3 = Ammonia (covalent) KOH = potassium hydroxide (ionic) NaOH = sodium hydroxide (ionic)

Recognizing Patterns: Acid-Base Conjugate Pairs always differ by an H+ Brønsted-Lowry Acids are proton (H+) donors. Bases are proton (H+) acceptors. HCl + H2O  Cl– + H3O+ acid conjugate base base conjugate acid

Recognizing Patterns: Conjugate Acid-Base Pairs Give the conjugate base for each of the following: HNO3 NO3 -1 C2H3O2H C2H3O2-1 HCl Cl-

Recognizing Patterns: Conjugate Acid-Base Pairs Give the conjugate acid for each of the following: Cl- HCl NH4+1 NH3 H2O OH -1

Example Reaction NH3 + HCl → Video Link

Amphoteric - can be an acid or a base. Water is amphoteric NH3 + H2O  B A Amphoteric - can be an acid or a base.

Water is amphoteric NH3 + H2O  NH4+ + OH- B A CA CB .

Water is amphoteric H2O + HNO3  A B

Water is amphoteric H2O + HNO3  H3O+ + NO3– B A CA CB

Ionic Bases: Must dissociate ions first NaOH (aq) + HCl(aq) → Ionic base Acid Na+1 OH-1 H+ Cl- H2O + Na+1 + Cl- or NaCl NaOH (aq) + HCl(aq) → H2O + NaCl HCl + NaOH

Recognizing Patterns: Conjugate Acid-Base Pairs Give the conjugate acid for each of the following: H2O NH3 OH- H3O+ NH4+ H2O