1. 1 Chapter 19 Acids, Bases, and Salts

2. 2 Section 19.1- Acid-Base Theories Objectives : –Define the properties of acids and bases. –Compare and contrast acids and bases as defined by the theories of Arrhenius and others

3. 3 Properties of Acids Taste tart or sour (don’t try this at home). –Vinegar – ethanoic acid –Lemon – citric acid Conduct electricity when in aqueous solution. –Can be strong or weak electrolytes in aqueous solution React with metals to form H 2 gas. React with bases (hydroxides) to form water and a salt.

4. 4 Properties of Acids Blue litmus paper turns red in contact with an acid.

5. 5 Properties of Acids Acids have a pH less than 7

6. 6 Properties of Bases Taste bitter. –Definitely do not try this at home! Feel slippery Can be strong or weak electrolytes in aqueous solution React with acids to form water and a salt Example of Bases Sodium hydroxide (lye or Drano), NaOH Magnesium hydroxide, Mg(OH) 2 - Milk of Magnesia Calcium hydroxide (lime water), Ca(OH) 2

7. 7 Properties of Bases Red litmus paper turns blue in contact with a base. Phenolphthalein turns pink in a base.

8. 8 Bases have a pH greater than 7 Properties of Bases

9. 9 Bases neutralize Acids Milk of Magnesia contains magnesium hydroxide, Mg(OH) 2, which neutralizes stomach acid, HCl. 2 HCl + Mg(OH) 2 MgCl 2 + 2H 2 O Properties of Bases Notice – a salt and water AcidBase

10. 10 Acids & Bases Chart

11. 11 19.2

12. 12 Section 19.2 - Hydrogen Ions and Acidity Objectives –Describe how [H 1+ ] and [OH 1- ] are related in an aqueous solution. –Classify a solution as neutral, acidic, or basic given the hydrogen-ion or hydroxide-ion concentration. –Convert hydrogen-ion concentrations into pH values and hydroxide-ion concentrations into pOH values. –Describe the purpose of an acid-base indicator.

13. 13 HOH ↔ H + + OH - At room temperature the molar concentration: hydrogen ions = 1 x 10 -7 M hydroxide ions = 1 x 10 -7 M –In pure water the concentration of H + and OH - are equal –An aqueous solution in which [H+] and [OH-] are equal is a neutral solution Hydrogen Ions from Water

14. 14 HOH ↔ H + + OH - –Acidic solution [H + ] is greater than [OH - ] [H + ] of an acidic solution is greater than 1 x 10 -7 M –Basic solution (AKA alkaline solution) [H + ] is less than [OH - ] [H+] of an alkaline solution is less than 1 x 10 -7 M Hydrogen Ions from Water

15. 15 The pH Scale The pH scale was devised to easily show how acidic or basic a solution is. –Used to express the hydrogen ion concentration pH means power of hydrogen  pH :  [H + ] :  [OH - ] : more acidic  pH :  [H + ] :  [OH - ] : more basic or alkaline.

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17. 17 The pH Scale In an acidic solution, pH < 7 In a basic solution, pH > 7 pH = -log[H + ] pH = -log(1 x 10 -7 ) –pH = 7 pH = -log(1 x 10 -9 ) –pH = 9

18. 18 Practice with the pH Scale What is the pH of a solution with [H + ] = 1 x 10 -2 ? What is the [H+] of a solution with a pH of 8? What is the [H+] of a solution with a pH of 9? The concentration of H+ in a solution with a pH of 8 is ___ times greater than the H+ concentration in a solution with a pH of 9? The [H+] in a solution with a pH of 2 is ___ times greater than the [H+] in a solution with a pH of 4? 10 2 1 x 10 -8 1 x 10 -9 100

19. 19 Measuring pH Why measure pH? –Maintaining proper acid-base balance in swimming pools, creating proper soil conditions for plant growth, and making medical diagnosis How do we measure pH? –Sometimes we can use indicators, other times we might need a pH meter Indicators –Substances that change color to show whether a substance is an acid or base –See Reference Table M for a list of Indicators

20. 20 Measuring pH 1. Moisten indicator strip with a few drops of solution, by using a stirring rod. 2. Compare the color to the chart on the vial – read the pH value.

21. 21 19.4

22. 22 Section 19.4 - Neutralization Reactions Objectives: –Define the products of an acid-base reaction. –Explain how acid-base titration is used to calculate the concentration of an acid or a base. –Explain the concept of equivalence in neutralization reactions. –Describe the relationship between equivalence point and the end point of a titration.

23. 23 Neutralization Reactions Remember, in a neutral solution [H+] = [OH-] So, if I mix a strong acid containing a certain number of H + ions with strong base that has an equal number of OH - ions, a neutral solution results HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H 2 SO 4(aq) + 2KOH (aq)  K 2 SO 4(aq) + 2H 2 O (l) Strong Acid with: 1000 H + ions Strong Base with: 1000 OH - ions [H+] = [OH-]: Neutral solution

24. 24 Neutralization Reactions Neutralization reactions produce water and a salt. Acid + Base  Water + Salt The salt forms from an anion from the acid and a cation from the base. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) H 2 SO 4(aq) + 2KOH (aq)  K 2 SO 4(aq) + 2H 2 O (l) acid base salt water

25. 25 Applications of Neutralization Reactions –Properties related to every day: Antacids depend on neutralization Farmers use these reactions to control soil pH Human body kidney stones from insoluble salts from neutralization reactions Acid + Base  Water + Salt

26. 26Titration

27. 27 How to Titrate an Unknown Acid A titration is a neutralization reactions. Here’s how it works: I have.2 liters of NaOH (base) but I don’t know how concentrated it is… …in other words I don’t know its molarity (moles/liter) Notice it’s clear

28. 28 How to Titrate an Unknown Base I want to know the molarity of this base, so I do a titration… Step 1 Step 1: Add a few drops of phenolphthalein –This solution is basic, so it will turn pink when I add phenolphthalein Notice it’s pink Dropper with phenolphthalein

29. 29 How to Titrate an Unknown Base Step 2 Step 2: Using a burette filled with a acid, slowly add acid to the beaker molarity –I need to know the molarity of the acid. volume –I need to know the volume of the acid. –Lets use 1 molar HCl for this example Burette filled with a acid (1M HCl)

30. 30 How to Titrate an Unknown Base Step 3 Step 3: STOPWhen the solution in the beaker just barely changes color – STOP you have just reached the equivalence point (moles of H + = moles of OH - ) What does the (just barely) color change mean? Solution has just barely reached the point where it is not longer basic, it is neutral, but not acidic Remember: phenolphthalein will change to colorless to indicate a neutral or acidic solution Burette filled with a base (1M HCl)

31. 31 How to Titrate an Unknown Acid Step 4 Step 4: Record how much of the base went from the burette into the beaker. –For this example, let’s say I used.15 liters of HCl Step 5 Step 5: Use the titration equation to determine the molarity of the unknown base Burette filled with a base (1M NaOH)

32. 32 Titration Equation This equation is found on Table T M A V A = M B V B M A = M Acid = molarity of H + M B = M Base = molarity of OH - The equation is actually M H + V H+ = M OH V OH

33. 33 Titration Equation M H + V H+ = M OH V OH In the above equation the M values are for [H + ] & [OH - ] not the molarity of the acids or bases

34. 34 Using Titration Equation for our Example M H + V H+ = M OH V OH (1M)(.15L) = (M OH )(.2L) (.15) =.2M OH.15 /.2 = M OH.75 moles of OH - per liter of solution The base is NaOH, there is: 1 “OH” in every 1 “NaOH” so… It is also.75 moles of NaOH per liter Remember: I used.15L of 1M HCl (acid) to neutralize.2L of ? M NaOH (base)

35. 35 moles of H+ vs moles of Acid moles of OH- vs moles of Base moles of H+ vs moles of Acid moles of OH- vs moles of Base Some acids have two or more moles of H + for every mole of acid. –H 2 SO 4 has 2 moles of H + for every 1 mole H 2 SO 4 Thus, 1.0M H 2 SO 4 has 2.0M H + The same is true for bases. –Ba(OH) 2 has 2 moles of OH - thus 1.0M Ba(OH) 2 has 2.0M OH -

36. 36 Titration Practice Problem If 15.0 ml of 2.00M H 2 SO 4 titrates 3.00M NaOH, what was the volume of NaOH? M H + V H+ = M OH V OH (4)(15) = (3)(V OH ) (60) = (3)(V OH ) 60/3 = V OH 20mL = V OH 2.00M H 2 SO 4 has 4.00 M H+ because every 1 mole H 2 SO 4 has 2 moles H+. Likewise, every 1 mole NaOH has only 1 mole OH -. FOR THIS PROBLEM - Molarity of NaOH solution is same as Molarity of OH -

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38. 38 Titration Practice Problem If 25.0 ml of 2.00M HCl titrates 30.0ml of NaOH, what is the molar concentration of NaOH? 2.00M HCl has 2.00 M H+ because every 1 mole HCl has 1 mole H+. Likewise, every 1 mole NaOH has 1 mole OH -. FOR THIS PROBLEM - Molarity of solution is same as Molarity of H+ and OH- ANSWER: 1.67 M OH- = 1.67 moles OH - / 1 Liter

39. 39 Videos Intro video (1:24 min): http://www.youtube.com/watch?v=S7CsO3p5t5Mhttp://www.youtube.com/watch?v=S7CsO3p5t5M Acids & Bases with Hannah & Kelsie (~3 min): http://www.youtube.com/watch?v=6fZ2OJ-HNr0&feature=relatedhttp://www.youtube.com/watch?v=6fZ2OJ-HNr0&feature=related Puppet Acid & base Video(6:56 min): http://www.youtube.com/watch?v=4cL1kmjASbY Richard Thorpe Acids & Bases: (~3:30 min): http://www.youtube.com/watch?v=JCcpWMW-SzY&feature=related http://www.youtube.com/watch?v=JCcpWMW-SzY&feature=related Water as an Acid & Base(8:44): http://www.youtube.com/watch?v=KSsS1jkBMnUhttp://www.youtube.com/watch?v=KSsS1jkBMnU Rainbow Connection with the Muppets(~3:22 min): (man) http://www.youtube.com/watch?v=lCrMB8341rUhttp://www.youtube.com/watch?v=lCrMB8341rU (female) http://www.youtube.com/watch?v=IUAa0usLZeU&feature=relatedhttp://www.youtube.com/watch?v=IUAa0usLZeU&feature=related Acid / base Indicators: http ://www.youtube.com/watch?v=6Y4Y-__ME60 (4:11 min)http ://www.youtube.com/watch?v=6Y4Y-__ME60 How to do a Titration Experiment(~2min): http://www.youtube.com/watch?v=r1uEXOOR2nU&feature=related World of Chemistry (the Proton in Chemistry (29:05 min): http://www.learner.org/resources/series61.html#http://www.learner.org/resources/series61.html# Neutralization reaction: http://www.youtube.com/watch?v=8IRI5gPR5EY (59 sec0http://www.youtube.com/watch?v=8IRI5gPR5EY Acid / base Neutralization: http://www.youtube.com/watch?v=enPG0vkn4QA (3:23 min)http://www.youtube.com/watch?v=enPG0vkn4QA Acid & Bases have two different Faces: http://www.youtube.com/watch?v=zTLiJE-j1-I (3:26 min)http://www.youtube.com/watch?v=zTLiJE-j1-I Kid mixing Vinegar & Baking Soda - http://www.youtube.com/watch?v=3hor1sePkfI (55 sec)http://www.youtube.com/watch?v=3hor1sePkfI Titrating an Acid http://www.youtube.com/watch?v=6woC_HSVtmQ (3:22 min)http://www.youtube.com/watch?v=6woC_HSVtmQ Titration of an Acid http://www.youtube.com/watch?v=yNSE_xa5lfA (1:22 min)http://www.youtube.com/watch?v=yNSE_xa5lfA How to Perform a titration: http://www.youtube.com/watch?v=YDzzMcrdyB4 (6:07 min)http://www.youtube.com/watch?v=YDzzMcrdyB4 Cool Universal Indicator Video http://www.youtube.com/watch?v=TXA9NNLrQFc (1:52 min)http://www.youtube.com/watch?v=TXA9NNLrQFc