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Understanding Acids and Bases: An In-depth Exploration

Dive into the world of acids and bases to unravel their chemical nature, properties, and behaviors. Learn how acids and bases interact, their dissociation in water, and the significance of pH in determining solution acidity.

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Understanding Acids and Bases: An In-depth Exploration

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  1. CHAPTER 13 Acids and Bases 13.1 The Chemical Nature of Acids and Bases

  2. Hydrochloric acid (HCl) is a strong acid in your stomach The acid in your stomach (HCl) can burn skin and dissolve metal! A base from the pancreas (HCO3–) helps to neutralize any acid that leaves the stomach What makes an acid an acid? What makes a base a base? Bicarbonate (HCO3–) ions are produced by the pancreas

  3. From Chapter 4 Higher H+ concentration Lower H+ concentration The pH scale helps to determine whether a solution is acidic or basic.

  4. H2O(l) H+(aq) + OH–(aq) Neutral solution: Neutral solution Dissociation of water: This equilibrium lies heavily on the reactant side Only 1 out of 550 million water molecules is dissociated into a hydrogen (H+) ion In neutral water or solution, the concentrations of H+ and OH– are equal

  5. Acidic solution: Acids An acid dissolves in water to create more H+ ions than there are in neutral water

  6. Acidic solution: Acids

  7. Basic solution: Bases Sodium hydroxide (NaOH) is also known as lye or caustic soda NaOH(aq) → Na+(aq) + OH–(aq) A base dissolves in water to create more OH– ions than there are in neutral water

  8. Basic solution: Bases

  9. Bases Potassium hydroxide (KOH) is used in alkaline batteries A base dissolves in water to create more OH– ions than there are in neutral water An alkaline substance is a salt of a group 1 or group 2 metal that dissolves in water to make a base.

  10. Arrhenius theory More H+ ions More OH– ions

  11. H+ is powerful because it has no electrons! Hydronium ion (hydrated proton) The hydronium ion The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” When we talk about H+ in water, we’re really talking about H3O+

  12. The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” (aq) NH3 + H2O NH4+ + OH– Ammonia is a proton acceptor so it is a base

  13. The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton.” HNO3→H+ + NO3– (aq) Nitric acid is a proton donor It is indeed an acid

  14. Acid-base pairs A proton that is donated by one chemical (an acid) must be accepted by another chemical (a base) Acids and bases always act in pairs called conjugate acid-base pairs!

  15. Acid-base pairs

  16. Acid-base pairs NH3 is the conjugate base of NH4+ NH4+ is the conjugate acid of NH3

  17. Acid-base pairs HCl is the conjugate acid of H3O+ H3O+ is the conjugate base of HCl

  18. NH3 + H2O NH4+ + OH– H+ donor (acid) HCl + H2O H3O+ + Cl– H+ acceptor (base) Water can act as either an acid or a base! amphoteric: a substance that can act as either an acid or a base under different circumstances.

  19. HCl(aq) →H+(aq) + Cl–(aq) hydrochloric acid H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) ascorbic acid (vitamin C) Identifying acids The H+ that gets donated is written first

  20. HCl(aq) →H+(aq) + Cl–(aq) 1 M 1 M H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) 1 M < 0.02 M Identifying acids A strong acid dissociates completely A weak acid dissociates only partially

  21. Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) calcium hydroxide Identifying bases The OH group at the end reminds chemists that a chemical is a base Not all bases have an OH group!

  22. Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) 1 M 2 M KOH(aq) → K+(aq) + OH–(aq) 1 M 1 M Identifying bases A strong base dissociates completely

  23. NH3(aq) + H2O(l) NH4+(aq) + OH–(aq) 1 M ~ 0.004 M Identifying bases A weak base yields much less than 1 OH– ion per molecule of base in solution. For example, 1 mole of ammonia (NH3) produces about 0.004 moles of OH– ions.

  24. Brøndsted-Lowry: pH range: [H+] and [OH–]: Arrhenius: Acids Bases produce H+ ions in aqueous solutions produce OH– ions in aqueous solutions donate H+ ions accept H+ ions pH < 7 pH > 7 [H+] > [OH–] [H+] < [OH–] Water can act as either an acid or a base The whole subject of acids and bases has to do with the extraordinary chemical power of the H+ ion, the “naked proton”

  25. H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) HCl(aq) →H+(aq) + Cl–(aq) 1 M < 0.02 M 1 M 1 M Strong: Complete dissociation Acids Weak: Partial dissociation

  26. H2C6H6O6(aq) →2H+(aq) + C6H6O6–(aq) HCl(aq) →H+(aq) + Cl–(aq) 1 M < 0.02 M 1 M 1 M Ca(OH)2(aq) → Ca2+(aq) + 2OH–(aq) 1 M 2 M NH3(aq) + H2O(l) NH4+(aq) + OH–(aq) 1 M ~ 0.004 M Strong: Complete dissociation Acids Weak: Partial dissociation Strong: Complete dissociation Bases Weak: Partial dissociation

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