Acid and Bases: An Introduction

Properties of Acids 1. Sour taste 2. Can produce H + (hydrogen) ions (protons) 3. Change the color of litmus from blue to red 4. Reacts with metals such as Zn and Mg to produce H 2 gas. Ba(s) + H 2 SO 4  BaSO 4 (aq) + H 2 (g) 5. Reacts with carbonates (CO 3 2- )to produce CO 2 NaHCO 3 (s) + CH 3 COOH(aq)  NaCH 3 COO(aq) + H 2 O(l) + CO 2 (g) 6. Acids conduct an electric current

Properties of Bases 1. Bitter or caustic taste 2. A slippery, soapy feeling 3. Can produce OH- (hydroxide) ions 4. Ability to change litmus from red to blue 5. Bases conduct an electric current 6. Bases react with acids to produce a salt and water. This is known as a neutralization reaction. HCl + NaOH  NaCl + H 2 O HCl + Mg(OH) 2  MgCl 2 + H 2 O acid base salt water

Ions in Solution Acidic solutions contains more hydrogen (H+) ions than hydroxide ions (OH-) pH < 7 Basic solutions contains more hydroxide ions (OH-) than hydrogen ions pH > 7 Neutral solutions contain an equal concentration of hydrogen and hydroxide ions pH = 7

Question Time What are the properties of acids? What are the properties of bases? What ion does an acid typically produce? What ion does a base typically produce? What is the OH- ion called? If there are more H + ions than OH -, is the solution acidic, basic, or neutral? What if there are an equal number of H + and OH - ions?

Three Definitions of Acids/Bases TypeAcidBase ArrheniusH + producerOH - producer Bronsted-LowryH + donorH + acceptor LewisElectron-pair acceptor Electron-pair donor

Bronsted-Lowry Conjugate Acid/Base HX(aq) + H 2 O(l) ⇆ H 3 O + (aq) + X - (aq) acid base Conjugate Conjugate Acid Base Conjugate acid is the substance produced when a base accepts a hydrogen ion from an acid Conjugate base is the substance that the acid donates a hydrogen ion to form a base

Bronsted-Lowry Conjugate Acid/Base Conjugate acid-base pair consists of two substances related to each other by donating and accepting of a single hydrogen ion NH 3 (aq) + H 2 O(l)  NH 4 + (aq) + OH - (aq) baseacid conjugate conjugate acid base

Practice: Conjugate Acid and Conjugate Base HCO H 2 S ⇆ H 2 CO 3 + HS - H 2 PO OH- ⇆ HPO H 2 O H 2 SO 4 + NH 3 ⇆ HSO NH 4 + HC 2 H 3 O 2 + H 2 O ⇆ H 3 O + + C 2 H 3 O 2 -

Question Time Name the three models of acids/bases. What is the Arrhenius model of acids/bases? What is the Bronsted-Lowry Model of Acid bases? What is a conjugate acid and a conjugate base?

Question Time Identify the acid, base, conjugate acid, and conjugate base in the Bronsted-Lowry reactions. 1. NH 3 + H 2 O ⇆ NH OH - 2. H 2 O + CH 3 NH 2 ⇆ OH - + CH 3 NH HF + H 2 O ⇆ H 3 O + + F - 4. HCOOH +CN - ⇆ HCOO- + HCN 5. NH CO 3 2- ⇆ NH 3 + HCO 3 -

Water in Acid/Base solutions Water and other substances can act as both acids and bases and are said to be amphoteric Hydronium ion = H 3 O + = H + (Remember H + is a proton) H 2 O(l) + H 2 O(l) ⇆ H 3 O + (aq) + OH - (aq)

Monoprotic and Polyprotic Acids Monoprotic acid donates one hydrogen ion Polyprotic acid donates more than one hydrogen ion

Question Time What is a Lewis acid? What is a Lewis base? What is the H 3 O + ion called? What is the shorthand way to write H 3 O + ? What is amphoteric? Give an example.

Clicker Time Which is not a property of acids? A. Changes litmus paper red to blue B. Sour taste C. Conducts an electrical current D. Reacts with metal to product H2 gas

Clicker Time Which is not a property of bases? A. Changes litmus paper red to blue B. Sour taste C. Feels slippery D. Reacts with acids to product salt and water.

Clicker Time What is an Arrhenius acid? A. Hydrogen ion donor B. Accepts an electron pair C. Produces hydrogen ions D. Produces a hydroxide

Clicker Time What is a Bronsted-Lowry base? A. Produces hydroxide ions B. A hydrogen ion acceptor C. An electron pair donor D. Produces hydrogen ions

Clicker Time What is a Lewis acid? A. A hydrogen ion producer B. A hydrogen ion donator C. An electron pair acceptor D. An electron pair donor

Clicker Time HNO 3 + H 2 O  NO H 3 O + Which substance is the acid? A. HNO 3 B. H 2 O C. NO 3 - D. H 3 O +

Clicker Time HNO 3 + H 2 O  NO H 3 O + Which substance is the conjugate base? A. HNO 3 B. H 2 O C. NO 3 - D. H 3 O +

Clicker Time HCl + NH 3  NH Cl - Which substance is the base? A. HCl B. NH 3 C. NH 4 + D. Cl -

Clicker Time HCl + NH 3  NH Cl - Which substance is the conjugate acid? A. HCl B. NH 3 C. NH 4 + D. Cl -