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Acids and Bases

Acids and Bases. Properties of Acids and Bases. Acids. Arrhenius Definition: Break apart (dissociate) to yield hydrogen ions (H + ) in water (aqueous) solutions HCl H + + Cl - HNO 3 H + + NO 3 - H 2 SO 4 H + + HSO 4 -. H 2 O. H 2 O.

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Acids and Bases

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  1. Acids and Bases

  2. Properties of Acids and Bases

  3. Acids • Arrhenius Definition: Break apart (dissociate) to yield hydrogen ions (H+) in water (aqueous) solutions HCl H+ + Cl- HNO3 H+ + NO3- H2SO4 H+ + HSO4 - H2O H2O H2O

  4. Naming Acids hydrochloric acid chloride hydro-(stem)-ic acid HCl (stem)-ous acid sulfite sulfurous acid H2SO3 (stem)-ic acid nitrate nitric acid HNO3

  5. Naming Acids Name the following acids: H2CrO4 HF H2CO3 HClO2 CH3COOH

  6. Writing Formulas of Acids Write the formulas for the following acids: Phosphorous acid

  7. Bases • Arrhenius Definition: Break apart (dissociate) to yield hydroxide ions (OH-) in water (aqueous) solutions NaOH Na+ + OH- KOH K+ + OH- H2O H2O

  8. Naming Bases NaOH sodium hydroxide Ca(OH)2 calcium hydroxide NH4OH ammonium hydroxide Cation name + hydroxide

  9. Naming Bases Name the following bases: Ba(OH)2 KOH Al(OH)3 Cation name + hydroxide

  10. More Naming Practice Name the following acids/bases or write their formula: H3PO4 Nitrous acid Mg(OH)2 Hydrobromic acid Lithium hydroxide H2S

  11. Even More Naming Practice! • Identify whether the following are acids or bases. Then name them! • Ba(OH)2 • 2. H2S • 3. CH3COOH • 4. Fe(OH)2 • 5. HClO2

  12. ThepHScale

  13. Remember the household products lab? • You tested household chemicals with litmus paper and pH paper.

  14. What happened to the pH paper? pH paper (aka Universal Indicator Paper) • What color(s) do/does the paper turn for acids? • What color(s) do/does the paper turn for bases? Reds and oranges GreensandBlues

  15. What is the pH scale? • pH: • stands for “potential of hydrogen” • represents the hydrogen ion (H+) concentration of a solution

  16. The pH scale Acidic solution: pH < 7.0 Neutral solution: pH = 7.0 Basic solution: pH > 7.0 Neutral ACIDIC BASIC pH = Increasing acidity Increasing basicity

  17. The pH Scale

  18. The pH Scale

  19. How can you tell the pH of a chemical? • Indicator paper (like pH paper) • Liquid indicators (like phenolphthalein) • pH meters Use an indicator!

  20. Indicators Indicator: a chemical or solution that changes color at a certain pH The pH range varies for different indicators

  21. LAB: Fruit and Vegetable Indicators Purpose: Many naturally colored compounds can behave as acid-base indicators. In this lab, you will be given a choice of several different fruits and vegetables. Your goal is to make indicators from these fruits and vegetables. Your goal today: - With your group, write a DETAILED procedure for how you will prepare your three fruit and vegetable indicator solutions. - Get approved by me before the end of the hour.

  22. Instructions: • Many naturally colored compounds can behave as acid-base indicators. In this lab, you will be given a choice of several different fruits and vegetables. Your goal is to make indicators from these fruits and vegetables. • On lined notebook paper, you must do the following: • Write a purpose. • Provide a complete set of instructions for making the indicator solution from the raw materials and testing the solution. (The indicator is usually in the skin of the fruit or veggie. You will have to boil the fruit or veggie in a small amount of water to extract the indicator). • Create a data table listing your results for 3 indicator solutions (see below). • Answer the analysis questions. • Available Materials: solutions with various pH, carrots, blueberries, red cabbage, red grapes, red onions, tea leaves, 100mL beaker, deionized water, pipettes, well plates, scoopula Indicator Lab

  23. DEMO • Why do chemistry teachers like to teach about hydroxides?

  24. Calculating pH and pOH

  25. H2O Acids • Recall that acids dissociate in water and give off H+ ions HCl H+1 + Cl-1

  26. [H+] = the hydrogen ion concentration IN MOLARITY pH What is an easy way of representing the concentration of hydrogen ions in a solution? pH (“potential of hydrogen”): a way of expressing the hydrogen ion concentration pH = - log [H+]

  27. Calculating pH Calculate the pH values using the equation pH = - log [H+]. Do you notice a pattern? 3.0 5.0 7.0 9.0 12.0 As the pH value increases, the H+ concentration decreases

  28. The pH Scale As the pH value increases, the H+ concentration decreases As the pH value decreases, the H+ concentration increases

  29. Calculating pH Example pH = - log [H+] What is the pH of a HCl solution in which [H+] = 3.9 x 10-4 M?

  30. [H+] = the hydrogen ion concentration IN MOLARITY Calculating [H+] How do we calculate the hydrogen ion concentration, [H+], if we know the pH? pH = - log [H+] [H+] = 10-pH

  31. Calculating [H+] Example [H+] = 10-pH What is the [H+] of a solution if the pH = 10.8?

  32. H2O Bases • Recall that bases dissociate in water and give off OH-1 ions NaOH Na+1 + OH-1

  33. [OH-] = the hydroxide ion concentration IN MOLARITY pOH Just like with pH… pOH (“potential of hydroxide”): a way of expressing the hydroxide ion concentration (the OH-) pOH = - log [OH-] Just like with [H+]: [OH-] = 10-pOH The only way to go between H and OH: pH + pOH = 14

  34. Example #1 What is the pOH of a solution if the [OH-] = 3.5 x 10-9 M?

  35. Example #2 What is the pH of a solution if the [OH-] = 0.00059 M?

  36. Example #3 What is the hydrogen ion concentration of a solution if the pOH is equal to 11.2?

  37. Acid-Base Neutralization Reactions

  38. Neutralization Reactions Remember double replacement reactions? HCl + NaOH → ____ + ____ To write balanced reaction: 1. Circle any polyatomic ions 2. Label charges 3. Write products – make charges cancel! 4. Balance using coefficients

  39. Neutralization Reactions Remember double replacement reactions? HCl + NaOH → ____ + ____ HCl + NaOH → NaCl + HOH All neutralization reactions will have this format… Acid + Base  Salt + water (H2O)

  40. Neutralization Reactions Practice #1 Name the acid and the base: HCl + Ca(OH)2 hydrochloric acid calcium hydroxide Complete and balance the neutralization reaction: HCl + Ca(OH)2 _____ + _____ 2HCl + Ca(OH)2 CaCl2 + 2H2O • Remember: • 1. Circle any polyatomic ions • 2. Label charges • 3. Write products – make charges cancel! • 4. Balance using coefficients

  41. Neutralization Reactions Practice #2 Name the acid and the base: H2SO4 + NaOH  sulfuric acid sodium hydroxide Complete and balance the neutralization reaction: H2SO4 + NaOH  _____ + _____ H2SO4 + 2NaOH  Na2SO4 + 2H2O • Remember: • 1. Circle any polyatomic ions • 2. Label charges • 3. Write products – make charges cancel! • 4. Balance using coefficients

  42. Neutralization Reactions Practice #3 Name the acid and the base: H2SO3 + NH4OH  sulfurous acid ammonium hydroxide Complete and balance the neutralization reaction: H2SO3 + NH4OH  _____ + _____ H2SO3 + 2NH4OH  (NH4)2SO3 + 2H2O • Remember: • 1. Circle any polyatomic ions • 2. Label charges • 3. Write products – make charges cancel! • 4. Balance using coefficients

  43. Neutralization Practice

  44. Neutralization Reactions Practice #4 Name the acid and the base: H3PO4 + LiOH  phosphoric acid lithium hydroxide Complete and balance the neutralization reaction: H3PO4 + LiOH  _____ + _____ H3PO4 + 3LiOH  Li3PO4 + 3H2O • Remember: • 1. Circle any polyatomic ions • 2. Label charges • 3. Write products – make charges cancel! • 4. Balance using coefficients

  45. Acid-Base Titrations

  46. Titrations Titration: adding a known amount of solution of known concentration to a solution with an unknown concentration Goal: To determine the unknown concentration of a solution

  47. Titrations Endpoint: the point of neutralization in a titration How do we know we reached the endpoint in a titration? We use an indicator and look for a color change!

  48. Titration Example A 2.5 L solution of H2SO4 is completely neutralized by 0.5 L of 1.0 M NaOH. What is the concentration of the H2SO4 solution? In buret: 1.0 M NaOH To solve this problem, we need to use the box method! In Erlenmeyer flask: ? M H2SO4

  49. A 2.5 L solution of H2SO4 is completely neutralized by 0.5 L of 1.0 M NaOH. What is the concentration of the H2SO4 solution? Step 1: Write the balanced neutralization equation. H2SO4 + 2 NaOH Na2SO4 + 2 H2O

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