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Acids and Bases

Acids and Bases. Chapter 19. Limestone is carved away by acid in rain to make these caves. . Ants use formic acid to alert each other of danger. Citrus acid gives OJ it’s flavor. What makes a solution acid or basic? Can something be neutral?.

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Acids and Bases

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  1. Acids and Bases Chapter 19

  2. Limestone is carved away by acid in rain to make these caves. Ants use formic acid to alert each other of danger. Citrus acid gives OJ it’s flavor.

  3. What makes a solution acid or basic?Can something be neutral? • Water, the most common solvent, breaks down into ions H2O H+ + OH- • The relative amounts of ions determine if a solution is acidic, basic or neutral • Acidic = more H+ (hydride) ions • Basic = more OH- (hydroxide ion) • Neutral = same amount of both (pH=7)

  4. Acids Contains more H+ Taste sour Corrosive to metals Changes litmus paper red Become less acidic when reacted with bases Forms hydrogen gas when reacted with metals pH 0-6.9 Bases Contains more OH- Taste Bitter Feel slippery Changes litmus paper blue Become less basic when reacted with acids pH 7.1-14 • Robert Boyle described differences between acids and bases

  5. Arrhenius acids • release hydrogen (H+) ions

  6. Arrhenius bases • release hydroxide (OH-) ions

  7. The Arrhenius theory doesn’t explain why some substances can act like a base even though they do not contain hydroxide ions • Johannes Bronsted and Thomas Lowry wrote independent papers to offer another explanation of acids and bases

  8. Bronsted-Lowry • Bronsted-Lowry Acid = any substance that can donate a hydrogen ion or a proton • Very similar to Arrhenius definition

  9. Bronsted-Lowry Base = any substance that can accept a hydrogen ion • Opposite of an acid • Explains why NaOH and KOH are considered bases b/c they accept a H+ from acid to form water • Also it explains why substance that do not contain OH- are still considered bases

  10. Conjugate Acids • Conjugate acid = formed from the base by addition of a proton (H+) • Base  conjugate acid

  11. Conjugate Bases • Conjugate base = formed from the acid by loss of a proton (H+) • Acid  conjugate base

  12. Conjugate acid-base pair consists of two substances related to each other by the donating and accepting of a single proton

  13. Water can act like both an acid and a base. • When substances can act as both an acid and a base they are called amphoteric

  14. The idea that a base can make an acid weaker and vice versa is called neutralization NaOH + HCl  NaCl + H2O

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