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Acid and Bases: An Introduction

Acid and Bases: An Introduction. Properties of Acids. Sour taste Can produce H + (hydrogen) ions (protons) Change the color of litmus from blue to red 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)

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Acid and Bases: An Introduction

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  1. Acid and Bases: An Introduction

  2. Properties of Acids • Sour taste • Can produce H+ (hydrogen) ions (protons) • Change the color of litmus from blue to red • Reacts with metals such as Zn and Mg to produce H2 gas. • Ba(s) + H2SO4 BaSO4(aq) + H2(g) • Reacts with carbonates (CO32-)to produce CO2 • NaHCO3(s) + CH3COOH(aq)  NaCH3COO(aq) + H2O(l) + CO2(g) • Acids conduct an electric current

  3. Properties of Bases • Bitter or caustic taste • A slippery, soapy feeling • Can produce OH- (hydroxide) ions • Ability to change litmus from red to blue • Bases conduct an electric current • Bases react with acids to produce a salt and water. This is known as a neutralization reaction. • HCl + NaOH  NaCl + H2O • HCl + Mg(OH)2 MgCl2 + H2O acid base salt water

  4. 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

  5. Three Definitions of Acids/Bases

  6. Bronsted-Lowry Conjugate Acid/Base • HX(aq) + H2O(l) ⇆ H3O+(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

  7. 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 • NH3(aq) + H2O(l)  NH4+ (aq) + OH-(aq) base acid conjugate conjugate acid base

  8. Practice: Conjugate Acid and Conjugate Base • HCO3- + H2S ⇆ H2CO3 + HS- • H2PO4- + OH- ⇆ HPO42- + H2O • H2SO4 + NH3⇆ HSO4- + NH4+ • HC2H3O2 + H2O ⇆ H3O+ + C2H3O2-

  9. 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?

  10. Question Time • Identify the acid, base, conjugate acid, and conjugate base in the Bronsted-Lowry reactions. • NH3 + H2O ⇆ NH4+ + OH- • H2O + CH3NH2⇆ OH- + CH3NH3+ • HF + H2O ⇆ H3O+ + F- • HCOOH +CN-⇆ HCOO- + HCN • NH4+ + CO32- ⇆ NH3 + HCO3-

  11. Water in Acid/Base solutions • Water and other substances can act as both acids and bases and are said to be amphoteric • Hydronium ion = H3O+ = H+ (Remember H+ is a proton) • H2O(l) + H2O(l) ⇆ H3O+(aq) + OH-(aq)

  12. Monoprotic and Polyprotic Acids • Monoprotic acid donates one hydrogen ion • Polyprotic acid donates more than one hydrogen ion

  13. Question Time • What is a Lewis acid? • What is a Lewis base? • What is the H3O+ ion called? • What is the shorthand way to write H3O+? • What is amphoteric? Give an example.

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