1 / 50

Notes Packet 1 Acids and Bases

Notes Packet 1 Acids and Bases. Question: What is an electrolyte?. Electrolytes As substances dissolve, ionic substances release free ions Ions carry a charge Electrolytes can therefore carry electricity How do we test for electrolyte solutions?. Properties of Acids An electrolyte

hleonard
Download Presentation

Notes Packet 1 Acids and Bases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NotesPacket 1Acids and Bases

  2. Question: What is an electrolyte? • Electrolytes • As substances dissolve, ionicsubstances release free ions • Ions carry a charge • Electrolytes can therefore carry electricity • How do we test for electrolyte solutions?

  3. Properties of Acids • An electrolyte • conducts electricity • Taste sour • Corrosive • breaks down materials • React with active metals to release hydrogen gas • Neutralize bases to form a salt and water

  4. Properties of Acids • Cause color changes in indicators • A chemical that reacts with an acid or base and shows a color change • blue litmus paper • changes to red • (aciD = reD) • phenolphthalein solution • changes to clear • Have a pH below 7 (more later!)

  5. Commonly used Acids Regents Chemistry Table K Common Acids • Monoprotic acid • only one H+ released • HCl, HNO3 • Diprotic acid • Two H+ ions released • H2CO3, H2SO4 • Triprotic acid • Three H+ ions released • H3PO4

  6. Properties of Bases • An electrolyte • conducts electricity • Taste bitter • Caustic • breaks down skin • Feel slippery because bases dissolve skin • Neutralize acids to form a salt and water

  7. Properties of Bases • Cause color changes in indicators • red litmus paper • changes to blue color • (Blue = Base) • Phenolphthalein solution • changes to pink color • Have a pH above 7 • Neutralize acids to form a salt and water

  8. Commonly used Bases Regents Chemistry • Monohydroxy base -only one OH- released • NaOH, KOH • Dihydroxy base -two OH- ions released • Ca(OH)2 • Ammonia – special case (more later) Table K Common Bases

  9. Acid Base TheoriesNote Packet 2

  10. Arrhenius Theory of Acids and Bases • An Acid is: • A substance that ionizes in water to produce hydrogen ions (H+) • H+ ions can’t exist alone • They combine with water to form hydronium ions (H3O+) HCl(g) H+(aq) + Cl–(aq) or H2O(l) + HCl(g) H3O+(aq) + Cl–(aq) • A Base is: • A substance that ionizes in water to produce hydroxide ions (OH-) NaOH(s) Na+(aq) + OH–(aq)

  11. Other Theories: • Bronsted-Lowry Theory of Acids • any substance that can donate or give up a proton (proton = H+ ion) • Example: NH4+ (ammonium) can donate a proton H20(l) + NH4+ NH3(aq) + H2O+(aq) • Bronsted Lowry Theory of Bases • any substance that can accept a proton • Usually have a free, unshared pair of electrons that the proton (H+) can attach to • NH3 (ammonia) has an unshared pair of electrons H2O(l) + NH3 NH4+ (aq) + OH-(aq)

  12. Amphiprotic or Amphoteric substances • Bronsted-Lowry Theory describessome molecules can act as either an acid or a base • They have hydrogen ions to give up like an acid • They have unshared electrons to absorb hydrogen ions like a base • Depending on what molecules they hook up with, they can act as either an acid or base

  13. Amphiprotic or Amphoteric substances • Examples • Water can donateoraccept a H+ ion H2O(l) + H2O(l) H3O+(aq) + OH-(aq) • Ammonia can donate a H+ ionlike an acid NH3(g) + H2O(g) NH2-(aq) + H3O+(aq) • or accept a H+ ion like a base NH3(g) + H2O(g) NH4+(aq) + OH-(aq)

  14. For each of the phrases below, write the correct number next to the phrase that indicates whether the compound described is: (1) AN ACID ONLY (3) AN ACID OR A BASE (2) A BASE ONLY (4) NEITHER AN ACID NOR A BASE. 1. Feels slippery to the touch _____ 2. Tastes bitter _____ 3. Contains some hydronium ions _____ 4. Increases the hydroxide ion concentration of water _____ 5. Increases the hydronium ion concentration of water _____ 6. Has a pH of 2 _____ 7. Product of a neutralization reaction _____ • Aqueous solution conducts electricity _____ • Turns phenolphthalein colorless _____ • The compound C2H5OH(aq) ______ • The compound NaOH(aq) ______ • The compound, HNO3(aq) ______ • The ion represented by the formula H3O+ ______

  15. Note Packet 3pH – how acidic or basic a substance is

  16. How does acid cause ulcers and heartburn? • Acids’ one major characteristic is that they are corrosive • This includes your stomach lining when you are stressed or eat overly spicey food • Why do acids have this characteristic? • Its all in their pH

  17. The pH scaleacid neutralbasic or alkaline

  18. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • REMEMBER = Water is polar • Slightly (+) hydrogens of one water molecule • Are attracted to (-) oxygens of another • Because of this, water ionizes (forms (+) and (-) ions) to a very small extent: H2O + H2O  H3O+ + OH– Acid part Base part of water of water

  19. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • For every water molecule that becomes an acid ion, one becomes a base ion • This evens out • for every H3O+ ion there is an OH– ion • When they combine, they make 2 water molecules • The concentration of the ions in pure water are: [H3O+] = 10–7 M or 0.0000001 M [OH–] = 10–7 M or 0.0000001 M

  20. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • The acid and base concentrations, when multiplied together, equals a constant value: [H3O+] = 10–7 M [OH–] = 10–7 M [H3O+] x [OH–] = 10–14 M • In any solution, including acids or bases • The concentration constant of [H3O+] x [OH–] is equal to 10-14 M

  21. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • In acids, there are more H3O+ ions (acid ions) than OH– ions (base ions) • Example • HCl is added to water. The H+ concentration rises to 10-4 M. What would the OH- concentration be? [H3O+ ] x [OH-] = 10-14 M 10-4 x [OH-] = 10-14 M [OH-] = 10-10 M • Note – the bigger the negative exponent, the smaller the amount you are dealing with • [H3O+ ] = 10-4 M = 0.0001 M • [OH-] = 10-10 M = 0.0000000001 M

  22. pH – how acidic or basic a substance is Symbol for concentration [ ] [X] = Concentration of X • In bases, there are more OH– ions (base ions) than H3O+ ions (acid ions) • Example • NaOH is added to water. The OH- concentration rises to 10-3 M. What would the H3O+ concentration be? [H3O+ ] x [OH-] = 10-14 M [H3O+ ] x 10-3 = 10-14 M [H3O+ ] = 10-11 M

  23. So where does pH come from??? • We said in the previous slides the following: • For water, • The [H3O+ ] was 10-7 and the [OH- ] was 10-7 • Its pH is 7, or NEUTRAL • For an acid, • The [H3O+ ] was 10-4 and the [OH- ] was 10-10 • Its pH is 4, or ACIDIC • For a base, • The [H3O+ ] was 10-11 and the [OH- ] was 10-3 • Its pH is 11, or Basic • So, to calculate pH, what do we look at?

  24. So, to calculate pH, what do we look at? • Example 1: a solution has a hydronium [H3O+ ] concentration 10-4 M. • What is the hydroxide [OH- ] concentration? • Remember: • [H3O+ ] x [OH- ] = 10-14 (a constant) • 10-4 M x [OH- ] = 10-14 • [OH- ] = 10-10 • What is the pH of the solution? • Look at the exponent of the [H3O+ ] • [H3O+ ] =10-4 = pH of 4 , acidic

  25. So, to calculate pH, what do we look at? • Example 2: a floor cleaning solution has a hydroxide [OH- ] concentration 10-6 M. • What is the hydronium [H3O+] concentration? • Remember: • [H3O+ ] x [OH- ] = 10-14 (a constant) • [H3O+ ] x 10-6 M x = 10-14 • [H3O+ ] = 10-8 • What is the pH of the solution? • Look at the exponent of the [H3O+ ] • [H3O+ ] =10-8 = pH of 8 , basic

  26. Unit Questions 1. In pure water, 10–7 M represents the concentration of (1) hydroxide only (3) both hydroxide and hydronium (2) hydronium only (4) neither hydroxide nor hydronium 2. The fact that the concentration of hydroniumand hydroxide are equal in pure water accounts for the fact that water is (1) neutral (2) an acid (3) a base • The pH of pure water is (1) 0 (2) 5 (3) 7 (4) 11 4. As the concentration of hydronium ions increases in water, the hydroxide ion concentration (1) increases (2) decreases (3) remain the same • When added to water, which of the following will cause the hydroxide ion concentration to increase? (1) NaCl (2) HCl (3) NaOH (4) HOH • An acid could have a pH of (1) 1 (2) 7 (3) 9 (4) 13 • A solution with a pH of 9 is (1) an acid (2) a base (3) neutral (4) a salt • Which of the following is NOT an acid? (1) HCl (2) HNO3 (3) H2SO4 (4) H2O 10. Which of the following solutions has the highest pH? (1) 1 M NaOH (2) 0.01 M NaOH (3) 1 M NaCl (4) 2 M HCl 11. What is the pH of a solution if [OH-] = 10-4 M? (1) 9 (2) 10 (3) 5 (4) 4

  27. Note Packet 4 Neutralization Reactions

  28. A student spills a container of acid on the floor. What does the student need to add to the acid to get rid of it? • Wipe it up? • Water it down? • What else could be done? • More than anything else - the acid needs to be neutralized

  29. What is Neutralization? • A DOUBLE REPLACEMENT reaction • Reacts an acid with a base to form a salt and water • General Equation: HA + BOH  HOH + BA Acid Base Water Salt • Example: NaOH + HCl  H2O + NaCl H2SO4 + 2 NaOH  2 H2O + Na2SO4

  30. Neutralization • Determine the products of each of the following neutralization reactions: 1. KOH + HBr  H2O + KBr 2. H2SO4 + Ca(OH)2  2H2O + CaSO4 • Spectator ions • ions that stay dissolved in the water of a solution, do not react • the ions that make up the soluble salts tend to be spectator ions

  31. Acid Base Indicators tell us how acid or basic a substance is • See Table M for examples of various indicators • The pH range on the chart represents the point that a color change will occur • Values to the left represent more acidic pHs • Values to the right represent more basic pHs

  32. Acid Base Indicator Examples 1. A solution leaves thymol blue a blue color and litmus paper changes to blue; is the solution basic or acidic? • Thymol is blue above the 8.0 – 9.6range • Litmus changes blue above the 5.5 – 8.2 range • Both show the solution above 8 • Solution is most likely basic 2. A solution changes methyl orange and litmus redand has no effect on phenolphthalein. Is it basic or acidic? • Methyl orange changes red below 3.2 – 4.4 • Litmus changes red below 5.5 - 8.2 • Both show the solution below 7 • Solution is most likely acidic

  33. Ma x Va = Mb x Vb Where: Ma = molarity of acid Mb = molarity of base Va = volume of acid used Vb = volume of base used Acid Base Titration • A method for determining the concentration or molarity of an unknown acid or base, based on the molarity of a known acid or base • Uses the process of neutralizationand the concept of endpoint • Endpoint: the point when the last of the acid and base are completely neutralized • Determined using an indicator to show the final neutralization point

  34. Problems 1. What substances form during an acid-base neutralization? (1) hydronium and hydroxide (3) acid and base (2) salt and water (4) metal and nonmetal 2. During the following acid-base neutralization, H2SO4 + Mg(OH)2 2H2O + MgSO4, what are the spectator ions? (1) H+ and OH– (3) Mg 2+ and SO4 2– (2) H3O+ and OH– (4) 2H2O 3. The table below shows the color of an indicator in specific pH ranges. If this indicator is used when titrating an unknown strong base by adding a strong acid, the color of the indicator will change from a.  blue to green b.  green to blue c.  orange to green d.  green to orange

  35. Titrations – Calculating StrengthsNote Packet 5

  36. Problems 1. What substances form during an acid-base neutralization? (1) hydronium and hydroxide (3) acid and base (2) salt and water (4) metal and nonmetal 2. During the following acid-base neutralization, H2SO4 + Mg(OH)2 2H2O + MgSO4, what are the spectator ions? (1) H+ and OH– (3) Mg 2+ and SO4 2– (2) H3O+ and OH– (4) 2H2O 3. The table below shows the color of an indicator in specific pH ranges. If this indicator is used when titrating an unknown strong base by adding a strong acid, the color of the indicator will change from a.  blue to green b.  green to blue c.  orange to green d.  green to orange

  37. How do we determine the acid’s or base’s strength (molarity) using our formula? • When enough known base is added to a sample of unknown acid in a titration • Endpoint is reached (the indicator in the sample changes color) • We now know • The molarity of the known base( Mb) • The volume of the base used = ( Vb) • The volume of the acid sample = (Va) • So we can calculate the molarity of the acid (Ma ) using the formula Ma x Va = Mb x Vb

  38. How do we determine the acid’s or base’s strength (molarity) using our formula? Example 1 – a 2.00 M acid solution is used to titrate an unknown base solution. If 40.00 mL of acid are used and 20.0 mL of base are used, what is the molarity of the base? Remember: M is molarity or concentration V is measured in mL or liters Ma x Va = Mb x Vb 2.00 M x 40.0 mL = Mb x 20.0 mL 4.00 M = Mb

  39. Example 2: Tropicana is having an issue with the citric acid levels in its new Tropicana Grapefruit Infused Fresh juice. A quality control chemist determines that 22 mL of an 1.0 M NaOH solution is used to neutralize 4400 mL of acidic TGIF juice. What is the molarity of the juice? Ma x Va = Mb x Vb Ma x 4400.0 mL = 1.00 M x 22.0 mL 0.005 M = Ma What is the pH of the Tropicana? .0050 M = 5.0 x 10-3 = pH of 3

  40. Example 3: A student performs a titration with a known base. She collects the data shown below. If the base has a molarity of 0.120 M, what is the molarity of the acid? How much acid How much base was used? was used? 42.4 mL – 22.4 mL 18.4 mL – 13.4 mL = 20.0 mL = 5.0 mL Ma x 20.0 mL = 0.120 M x 5.0 mL Ma = 0.030 M

  41. Acid / Base Strengths • HCl and H2SO4 release different numbers of H+ ions! • In the neutralization of NaOH, H2SO4 + 2NaOH  2H2O + Na2SO4 • NaOH and Ba(OH)2 also release different numbers of OH- ions! • In the neutralization of Ba(OH)2Note: 2HCl + Ba(OH)2 2H2O + BaCl2

  42. Problems 1. The double replacement reaction used to change an acid and a base to a salt and water is called (1) oxidation-reduction (3) condensation polymerization (2) neutralization (4) titration 2. What is the concentration of an H2SO4 solution if 10.0 mL of it can be neutralized by 15.0 mL of 2.0 M Ca(OH)2? (1) 1.5 M (2) 3.0 M (3) 10.0 M (4) 12.5 M 3. How much 6.0 M HCl is needed to neutralize 90. mL of 2.0 M KOH? (1) 30 mL (2) 7.5 mL (3) 270 mL (4) 78 mL 4. A technique used to determine the concentration of a base using a standard solution of an acid is known as (1) ionization (2) neutralization (3) molarity (4) titration 5. What is the concentration of an H2SO4 solution if 10.0 mL of it can be neutralized by 15.0 mL of 2.0 M NaOH? (1) 1.5 M (2) 3.0 M (3) 10.0 M (4) 12.5 M

  43. Real World Applications of Acids and BasesNote Packet 6

  44. Real World Acid/Base Applications • Acid Rain • Forms from the reactions of sulfur and nitrogen oxides reacting with moisture in the air • Increases the acidity of rainwater • Falls into lakes and ponds • Eats at metals in the lakebeds, ionizing them and polluting the lakes and ponds • Remediation – add lime (base material) to neutralize the acid in the lake – expensive!

  45. Real World Acid/Base Applications • A lake has an acid molarity of 0.00005 M for every 1000 mL. How much of a 0.001 M lime solution is needed to neutralize this amount of acidic lake water? Ma x Va = Mb x Vb 0.00005 M x 1000 mL = 0.001 M x Vb 50 mL = Ma

  46. Uses of Acids • CH3COOH - Acetic acid • Vinegar in very dilute solution form (3% solution) • HCl – hydrochloric acid • pH control for swimming pools • Cleaning material for tiles "muriatic acid“ • H2SO4 - sulfuric acid • battery acid in your car • HNO3 – nitric acid • Reaction with ammonia to make fertilizers • Reaction with glycerol and toluene to make TNT • H3PO4 – phosphoric acid • can be used to remove rust

  47. Uses of Bases • NaOH – sodium hydroxide • one of the most used bases in industrial processes, also called "lye" and is in some soaps • can be used as a drain cleaner • NH3 – ammonia • most common use as a home cleaner • Used in the production of fertilizers • NaHCO3 - sodium bicarbonate • is present in most baking powder • CaO – calcium oxide – when mixed with water, creates Ca(OH)2 – calcium hydroxide • used in plaster, called quicklime

  48. Problems Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person's diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C6H8O6 and a gram-formula mass of 176 grams per mole. • What is the color of the indicator thymol blue after it is added to an aqueous solution of vitamin C? • A glass of orange juice has a total volume of 0.200 liters. What is the molarity of vitamin C if the molarity of a known base is .0100 M and the volume used to titrate is 0.002 liters? • What is the pH of this solution? • How many moles are in this sample?

More Related