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Acids and Bases Introduction

Acids and Bases Introduction. Chem 12 Chapter 14 Pg 544-559. Properties of Acids. Turn blue litmus paper red Neutralize the properties of bases React with certain metals to produce hydrogen gas React with carbonate compounds to produce carbon dioxide gas Have a sour taste

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Acids and Bases Introduction

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  1. Acids and Bases Introduction Chem 12 Chapter 14 Pg 544-559

  2. Properties of Acids • Turn blue litmus paper red • Neutralize the properties of bases • React with certain metals to produce hydrogen gas • React with carbonate compounds to produce carbon dioxide gas • Have a sour taste • Are electrolytes • Have a pH less than 7

  3. Properties of Bases • Turn red litmus paper blue • Turn the indicator phenolphthalein from colorless to red • Neutralize the properties of acids • Have a bitter taste • Are electrolytes • Are slippery to the touch • Have a pH greater than 7

  4. Common Acids Battery acid Sulfuric Acid H2SO4 Nitric Acid HNO3 Phosphoric Acid H3PO4 Hydrochloric Acid HCl Acetic Acid CH3COOH Carbonic Acid H2CO3 Used to make fertilizers and explosives Food flavoring Stomach acid Vinegar Carbonated water

  5. Common Bases Name Formula Common Name Sodium hydroxide NaOH lye or caustic soda Potassium hydroxide KOH lye or caustic potash Magnesium hydroxide Mg(OH)2 milk of magnesia Calcium hydroxide Ca(OH) 2 slaked lime Ammonia water NH3 H2O household ammonia .

  6. Definition of Acid • An operational definition is a definition based on observed experimental properties. • An operational definition of an acid is that it is a substance that turns blue litmus paper red and has a pH less than 7.

  7. An operational definition of a base is that it is a substance that turns red litmus paper blue and has a pH greater than 7.

  8. A conceptual definition attempts to explain why a substance behaves the way it does. • Arrhenius theory (only applies to solutions made with water) and Bronsted-Lowery acid base definitions are conceptual

  9. Arrhenius Acid-Base Theory • An acid is a substance that produces hydrogen ions, H+ (aq), in water. Hydrogen ions always combine with at least one water molecule to produce hydronium ions, H3O+ HCl(g) + H2O(l) < -- > H3O+ (aq) + Cl-(aq) Arrhenius acid (hydrochloric acid)

  10. Arrhenius Base • A base is a substance that produces hydroxide ions, OH- (aq), in water. NaOH(s) + H2O(l) → Na+ (aq) + OH-(aq) Arrhenius base (sodium hydroxide)

  11. According to the Arrhenius acid-base theory, the hydronium ion explains the chemical properties of an acid, and the hydroxide ion explains the chemical properties of a base. • acid-base neutralization the hydronium ion from the acid reacts with the hydroxide ion from the base to produce water. H3O+(aq) + OH-(aq) → 2H2O(l)

  12. Brønsted-Lowry acid-base theory • An acid is proton (H+ ion) donor, and a base is a proton (H+ ion) acceptor. • This is a better definition because it is not limited to solutions where water is the solvent. Acid (proton donor) Base (proton acceptor)

  13. Monoprotic Acids • Bronsted-Lowry acids can be monoprotic-capable of losing one proton, such as: HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq) HNO3(aq) + H2O(l) H3O+(aq) + NO3-(aq)

  14. Bronsted-Lowry acids can also be polyprotic-capable of losing (donating) more than one proton. • Polyprotic acids lose their protons in separate steps or reactions.

  15. Diprotic Acids • Diprotic acids are capable of losing two protons. H2SO4(aq) + H2O(l) HSO4-(aq) + H3O+(aq) HSO4-(aq) + H2O(l) SO42-(aq) + H3O+(aq)

  16. Polybasic Bases • Bronsted-Lowry bases can be monobasic-capable of supplying one hydroxide ion such as NaOH(s) + H2O(l) Na+(aq) + OH-(aq)

  17. Polybasic basescan be capable of supplying more than one hydroxide ion. • Dibasic are capable of supplying two hydroxide ions. Mg(OH)2(s) + H2O(l) Mg2+(aq) + 2OH-(aq)

  18. Conjugate Acid-Base Pairs • A pair of substances that only differ by one proton. • Conjugate = “linked together” H+ donor NH4+ + CO3-2 < -- > NH3 + HCO3- Acid base conjugate conjugate base acid

  19. Conjugate acid and base, HA/A-, differ by one proton. The conjugate acid of a base is the base plus the attached proton and the conjugate base of an acid is the acid minus the proton.

  20. Conjugate Acid-Base Pairs Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280

  21. Amphoteric • Substances that can act like an acid in one reaction, and like a base in another type of reaction. • Example: baking soda’s anion HCO3- • HCO3- + OH- < -- > CO3-2 + H2O (donates a H+, so acts like an acid) • HCO3- + H3O+ < -- > H2CO3 + H2O (accepts a H+, so acts like a base)

  22. Practice: Finish these questions for homework Page 557 #1-9

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