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Acids and Bases

Acids and Bases. Definitions of Acids. Arrhenius Acid-any substance that produces hydrogen ions (H + ) when dissolved in water. Bronsted Lowry acid-any substance that donates protons to form hydronium ions (H 3 O + ) Examples of acids: HCl, HNO 3 , H 2 SO 4 , HC 2 H 3 O 2. Properties of Acids.

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Acids and Bases

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  1. Acids and Bases

  2. Definitions of Acids • Arrhenius Acid-any substance that produces hydrogen ions (H+) when dissolved in water. • Bronsted Lowry acid-any substance that donates protons to form hydronium ions (H3O+) • Examples of acids: HCl, HNO3, H2SO4, HC2H3O2

  3. Properties of Acids • Taste sour • React with metals • Conduct electricity • pH<7 • Turn litmus red • Turn phenolphthalein colorless

  4. Definitions of Bases • Arrhenius Base-any substance that produces hydroxide ions (OH-) when dissolved in water. • Bronsted Lowry Base- any substance that accepts protons. • Examples of bases: NaOH, Ca(OH)2, Mg(OH)2, NH3

  5. Properties of Bases • Taste bitter • Feel slippery • Conduct electricity • pH>7 • Turn litmus blue • Turn phenolphthalein pink

  6. 10 NaOH is an example of a(n) • Acid • Base • Neither

  7. 10 A substance that is a proton acceptor is a(n) • Acid • Base • neither

  8. HCl is an example of a(n) 10 • Acid • Base • Neither

  9. Lemon juice is an example of a(n) 10 • Acid • Base • Neither

  10. A substance that is a proton donor is an example of a(n) 10 • Acid • Base • Neither

  11. Drain cleaner is an example of a(n) 10 • Acid • Base • Neither

  12. Vinegar is an example of a(n) 10 • Acid • Base • Neither

  13. Water is an example of a(n) 10 • Acid • Base • Neither

  14. A substance that turns litmus red is a(n) 10 • Acid • Base • Neither • Both

  15. A substance that conducts electricity is a(n) 10 • Acid • Base • Neither • Both

  16. pH Scale

  17. Calculating pH • The pH scale is a logarithmic scale used to quantitatively represent the strength (concentration) of an acid. • pH = -log[H+] • The greater the concentration of the hydrogen ion (H+), the stronger the acid and the lower the pH.

  18. Sample Problems • What is the pH of a solution in which [H+] = 1 x 10-2? • pH = 2 • What is the pH of a solution in which [H+] = 1 x 10-6? • pH = 6 • Which is more concentrated? • pH=2

  19. pH and pOH • The pOH scale is a logarithmic scale used to quantitatively represent the strength (concentration) of a base. • pOH = -log[OH-] • The greater the concentration of the hydroxide ion (OH-), the stronger the base and the lower the pOH. • pOH + pH = 14

  20. Practice Problems • Calculate the pH and pOH of solutions with the following concentrations and classify as acidic, basic, or neutral. • [OH-] = 1 x 10-9 • [H+] = 1 x 10-7 • [H+] = 1 x 10-4 • [OH-] = 1 x 10-2

  21. Indicators and pH • Indicators are substances that change color depending on the concentration of hydrogen ions (H+) in a solution. • Litmus and phenolphthalein are examples of indicators. • Indicators can be used to determine the pH of a solution. • http://www.explorelearning.com/

  22. A solution with a pH of 3 is 10 • Acidic • Basic • Neutral

  23. Which of the following is an expected pH for a sample of lemon juice? 10 • 3 • 6 • 7 • 10

  24. A substance with a pH of 12.7 is a(n) 10 • Acid • Base • Neither • Both

  25. A solution with a [H+] =1x 10-5 has a pH of 10 • 1 • 5 • 9 • 14

  26. A solution with a pH of 8 has a pOH of 10 • 2 • 6 • 8 • 14

  27. A solution with a [OH-]=1x10-3 has a [H+] = 10 • 3 • 11 • 1 x 1011 • 1 x 10-11

  28. Naming Acids • Binary acids- consist of hydrogen and one other element. • Use the prefix –hydro and change the ending of the element to –ic. • Example: HCl hydrochloric acid HBr hydrobromic acid H2S hydrosulfuric acid

  29. Naming acids • Oxyacids-consist of hydrogen, oxygen, and one additional element. • If the polyatomic ion ends in –ate, change the ending to –ic. • If the polyatomic ion ends in –ite, change the ending to –ous. • Example: H2SO4 sulfuric acid (diprotic) H2SO3 sulfurous acid (diprotic) HNO3 nitric acid (monoprotic) HNO2 nitrous acid (monoprotic) H3PO4 phosphoric acid (triprotic)

  30. Naming bases • All bases consist of the hydroxide ion and one additional element. • Name the element followed by hydroxide. • Example: NaOH sodium hydroxide Ca(OH)2 calcium hydroxide Al(OH)3 aluminum hydroxide

  31. Which of the following is the correct name of HBr? 10 • Hydrobromic acid • Bromic acid • Bromous acid • Bromine hydroxide

  32. Which of the following is the correct name of H2CO3? 10 • Hydrocarbonic acid • Carbonic acid • Carbonous acid • Hydrogen coarbon oxide

  33. Which of the following is the correct name of Ba(OH)2? 10 • Hydrobaric acid • Baric acid • Barous acid • Barium hydroxide

  34. Neutralization Reactions • Neutralization reactions occur when acids react with bases and produce a salt and water. • A salt is an ionic compound consisting of the positive ion of the base and the negative ion of the acid. • Example: HCl + NaOH  NaCl + H2O acid base salt water • If the [H+] = [OH-], the resulting solution will be neutral (pH=7). • Neutralization reactions are a specific type of double displacement reaction.

  35. What salt is formed? • HCl + KOH  • H3PO4 + NaOH  • Ca(OH)2 + H2SO4  • Mg(OH)2 + HF  • HNO3 + NaOH 

  36. Titration • A titration is a method for determining the concentration of a solution by reacting a known volume of that solution with a solution of known concentration. • The reaction that takes place is a neutralization reaction.

  37. Procedure for carrying out titrations. • A measured volume of an acid or base is added to a beaker or flask. • A buret is filled with a solution of known concentration (titrant). • The solution of known concentration is added until the solution in the beaker has been completely neutralized. • This point is called the equivalence point.

  38. Titrations Continued • You will recognize the equivalence point because the indicator will change colors at this point. • This is also referred to as the end point of the titration. • The volume that is added to reach this point is used to calculate the unknown molarity.

  39. Example • 25.0 mL of HCl is titrated to the endpoint with 50.0 mL of 2.0 M NaOH. What is the molarity of the HCl? • M x V = M x V • X (25.0) = 2.0 (50.0) • X= 4.0 M

  40. http://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s5_5.swfhttp://www.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s5_5.swf

  41. Pre-lab: Which is the most effective antacid? • What makes an antacid effective? • How does the antacid affect the acid? • How will you determine which antacid is most effective at neutralizing the stomach acid?

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