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Acids, Bases, and pH

Acids, Bases, and pH. Chapter 9 Section 1. D12. Explain the chemical composition of acids and bases, and explain the change of pH in neutralization reactions. Learning Target. I can differentiate between acids and bases. Acids. When dissolved in water, they ionize (form ions)

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Acids, Bases, and pH

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  1. Acids, Bases, and pH Chapter 9 Section 1

  2. D12 • Explain the chemical composition of acids and bases, and explain the change of pH in neutralization reactions.

  3. Learning Target • I can differentiate between acids and bases.

  4. Acids • When dissolved in water, they ionize (form ions) • Form H+ (Hydrogen) ions, which attach to water molecules to form hydronium ions, H3O+ • Properties: • Taste sour • Blue litmus paper turns red • Conduct electric current • Corrosive

  5. Strong and Weak Acids

  6. HNO3 + H2O H3O+ + NO3- Strong Acids • Complete ionization in water • High concentration of hydronium ions in the liquid • Strong acid • Conducts electricity • Strong electrolyte

  7. CH3COOH + H2O H3O+ + CH3COO- Weak Acids • Weak acids • Low concentration of hydronium ions in the liquid • Do not conduct electricity well • Weak electrolyte • Double headed arrow

  8. Acid Safety • Corrosive • Can damage living tissues • Vapors can be harmful to eyes, mouth and lungs • Wear safety goggles, gloves, lab apron

  9. Bases • When dissolved in water form OH- (hydroxide ions) • Properties • Tastes bitter • Solution feels slippery • Turn red litmus paper blue • Like acids, bases can also damage the skin

  10. Strong and Weak Bases

  11. Bases • When bases dissolve in water, they ionize. NaOH Na+ + OH- • Not all bases contain OH- • Some will react with water to form hydroxide ion NH3 + H2O NH4+ + OH-

  12. Strong Bases • High concentration of OH- in the solution Ba(OH)2 Ba2+ + 2OH- • Complete ionization in water • Good conductor of electricity • Strong electrolyte

  13. Weak Bases • Low concentration of OH- in solution NH3 + H2O NH4+ + OH- • Do not ionize completely • Not a good conductor of electricity • Weak electrolyte

  14. Base Safety • Bases are corrosive and can damage living tissue • Wear safety goggles, gloves and a lab apron!!

  15. Let’s Review • What ions do acids produce? • What ions do bases produce? • What is the difference between a strong acid and a weak acid? • Why should we observe lab safety rules when working with acids and bases?

  16. Learning Target • I can explain pH.

  17. Detecting Acids and Bases • You can determine if a substance is an acid or a base by using an indicator. • An indicatoris a substance that changes color in the presence of an acid or base. • Indicators measure the level of hydronium ions. The level determines if a substance is acidic or basic.

  18. Indicators • Cabbage juice can be used as an indicator • Litmus paper is a common indicator • Acids turn blue litmus paper red • Bases turn red litmus paper blue • Only indicates if a substance is an acid or a base • To determine strength or weakness, pH values are used catalog.flatworldknowledge.com profmarsolais.com

  19. pH • A measure of the concentration of H3O+ ions in solution • Acidity or basicity of a solution can be critical • Enzymes in your body will not function properly if your blood is too basic or acidic • Fish cannot survive in waters that are too acidic or basic ck12.org hapnotes.wikidot.com

  20. Acid:substance that produces H+ ions in aqueous solution Base:substance that produces OH- ions in aqueous solution Neutral Pure H2O Ion Concentration Ion Concentration [OH-] [H+] Stronger Weaker Weaker Stronger 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Bases Acids pH Scale

  21. pH • Small differences in pH mean large differences in acidity • Example: pH of coke = 3 pH of coffee = 5 Coke is 102 , or 100, times more acidic than coffee. ch302.cm.utexas.edu

  22. gizmodo.com

  23. Let’s Review Lemon juice has a pH of 2.2. Is it an acid or a base?

  24. Detergents such as Tide have a pH of about 10. Is Tide an acid or a base?

  25. Seawater has a pH of 8.2. Is seawater an acid or a base?

  26. The inside of your mouth has a pH of 7. Is it an acid or a base?

  27. 409 cleaner contains ammonia that has a pH of 12. What will 409 do to red litmus paper?

  28. A soft drink has a pH of 3.2. What will it do to a piece of red litmus paper?

  29. Determining pH • You can find pH from the concentration of a strong acid. • pH is the negative power of 10 that is used to describe the concentration of H3O+ ions. The concentration of H3O+ in pure water is 1 x 10-7. The pH of pure water = 7

  30. Determining pH • The concentration of H3O+ ions in a solution of a strong acid is the same as the concentration of the acid. • Determine the pH of a 0.0001 M (Molar) solution of the strong acid HCl. concentration of H3O+ ions = concentration of HCl concentration of H3O+ ions = 0.0001 M = 1 x 10-4 M pH = -(-4) = 4

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