 Both acids and bases ionize or dissociate in water  Acids: taste sour, conduct electricity, cause certain indicators to change color,turn blue litmus paper red, and react with metals to form H 2 gas  Bases: taste bitter, feel slippery, conduct electricity, and cause certain indicators to change color, turn red litmus paper blue

An unknown solution conducts electricity. Upon further testing, scientists find that hydrogen gas is emitted when it is dropped onto magnesium ribbon. Classify the substance according to its properties. A.) Acid B.) Base

 Arrhenius definition for acid: compound that produces hydrogen ions (H + ) when dissolved in water.  Ex. HCl(g) is named hydrogen chloride. BUT HCl(aq) is named hydrochloric acid.  Let’s write the dissociation reaction for the HCl example. HCl + H 2 O  H + + Cl -

 Arrhenius definition of base: a compound that produces hydroxide ions (OH-) when dissolved in water.  Ex. NaOH(s) is named sodium hydroxide and is NOT a base. BUT NaOH (aq) is named sodium hydroxide and IS a base.  Let’s write the dissociation reaction for the NaOH example. NaOH + H 2 O  Na + + OH -

Which of the following aqueous solutions is an Arrhenius acid? A.) BaH2 B.) Ba(OH)2 C.) HBr D.) Both a and c

 Acids are hydrogen-containing compounds that ionize to yield hydrogen ions in aqueous solution...  Bases are compounds that ionize to yield hydroxide ions in aqueous solution...  BUT, NH 3 is a base! Arrhenius’ theory doesn’t hold up in every case, so...

 An acid is a hydrogen-ion donor, and a base is a hydrogen-ion acceptor.  Example: NH 3 (aq) + H 2 O(l)  NH 4 + (aq) + OH - (aq)  Analyze the compounds as they react. What happens during the reaction?  NH 3 accepts an H + to become NH4 +  H 2 O donates an H + to become OH -

 According to this theory, an acid has a conjugate base. Likewise, a base has a conjugate acid.  We refer to them as conjugate acid-base pairs. The two differ only by a hydrogen.  Example: NH 3 and NH 4 +, H 2 O and OH -

 H 2 SO 4 + H 2 O  H 3 O + + HSO 4 -  Label the acid, base, conjugate acid, and conjugate base.  Write conjugate acid-base pairs.

Which of the following substances is the acid in the H 2 SO 4 dissociation example? A.) H 2 SO 4 B.) H 2 O C.) H 3 O + D.) HSO 4 -

 Find the “Bronsted-Lowry Acids and Bases Practice Problems” worksheet in your practice packet.  Answer Part I.

 Identifying acid-base pairs in dissociation reactions can be a bit confusing at first.  Remember, the acid and base will be found in the reactants. The conjugate acid and base will be found in the products.  The acid will donate an H+ to become the conjugate base. The two substances will differ by ONLY one H+. Therefore, the acid will have one additional H+.  The base will accept an H+ to become the conjugate acid. The two will differ by ONLY one H+. Therefore, the conjugate acid will have one additional H+.  Complete Parts II and III of the “Bronsted-Lowry Acids and Bases Practice Problems” now.