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Chapter 14 Acids and Bases

Acids produce hydrogen ions in aqueous solution. Chapter 14 Acids and Bases. 14.3 Strengths of Acids and Bases. A final thought A Peanuts cartoon showed one of the others (Linus?) asking the awful Lucy why the sky was blue. The conversation went something like this:

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Chapter 14 Acids and Bases

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  1. Acids produce hydrogen ions in aqueous solution. Chapter 14 Acids and Bases 14.3 Strengths of Acids and Bases

  2. A final thought • A Peanuts cartoon showed one of the others (Linus?) asking the awful Lucy why the sky was blue. The conversation went something like this: • Linus: "Why is the sky blue?" • Lucy: "BECAUSE IT ISN'T GREEN!" • Linus: "Oh . . . I thought the reason would be much more complicated than that." • Make of that what you will!

  3. Strengths of Acids • A strong acid ionizes (100%) in aqueous solutions. HCl(g) + H2O(l) H3O+ (aq) + Cl- (aq) • A weak acid dissociates only slightly in water to form an aqueous solution containing mostly molecules of acid and a few ions. H2CO3(aq) + H2O(l) H3O+(aq) + HCO3− (aq)

  4. Strong and Weak Acids In solution, • hydrochloric acid, HCl, a strong acid, dissociates 100% • acetic acid, CH3COOH, a weak acid, contains mostly molecules and a few ions

  5. Strong Acids Strong acids • make up six of all the acids • have weak conjugate bases

  6. Weak Acids Weak acids • make up most of the acids • have strong conjugate bases

  7. Bases in household products are used to remove grease and to open drains. Strong Bases Strong bases • are formed from metals of Groups 1A (1) and 2A (2) • include LiOH, NaOH, KOH, and Ba(OH)2 • dissociate 100% in water KOH(s) K+(aq) + OH−(aq)

  8. Weak Bases Weak bases • are poor acceptors of protons • dissociate only slightly in water • produce only a few ions in water • are used in household products such as cleaners NH3(g) + H2O(l) NH4+(aq) + OH−(aq)

  9. Learning Check Identify each of the following as a strong or weak acid or base: A. HBr B. HNO2 C. NaOH D. H2SO4 E. Cu(OH)2

  10. Solution A. HBr strong acid B. HNO2 weak acid C. NaOH strong base D. H2SO4 strong acid E. Cu(OH)2 weak base

  11. Learning Check A. Identify the stronger acid in each pair. 1. HNO2 or H2S 2. HCO3- or HBr 3. H3PO4 or H3O+ B. Identify the stronger base in each pair. 1. NO3- or F- 2. CO32- or NO2- 3. OH- or H2O

  12. Solution A. Identify the stronger acid in each pair. 1. HNO2 2. HBr 3. H3O+ B. Identify the stronger base in each pair. 1. F- 2. CO32- 3. OH-

  13. http://www.chemguide.co.uk/index.html#tophttp://www.chemguide.co.uk/inorganic/group7/acidityhx.htmlhttp://www.chemguide.co.uk/index.html#tophttp://www.chemguide.co.uk/inorganic/group7/acidityhx.html The values for T x dS (needed to calculate dG) for the four reactions at a temperature of 298 K are:

  14. However, the terms involving the hydrogen will be the same for every hydrogen halide. So if we are just trying to draw comparisons, we only need to look at the terms shown in red in the diagram. If you compare the total HF and HCl values, there is virtually no difference.

  15. Putting all this together, what is the effect on the free energy change, and therefore the value of the equilibrium constant for the reaction?

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