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Acids and Bases – Unit 13

Acids and Bases – Unit 13. Unit 11 – Acids and Bases Notes #1: Intro. Acids : Something that produces a hydrogen ion (H + ) in solution. Properties of Acids : Tart or sour taste (lemon juice) Electrolytic Both strong and weak Will cause indicators to change colors

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Acids and Bases – Unit 13

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  1. Acids and Bases – Unit 13

  2. Unit 11 – Acids and BasesNotes #1: Intro Acids: Something that produces a hydrogen ion (H+) in solution

  3. Properties of Acids: • Tart or sour taste (lemon juice) • Electrolytic • Both strong and weak • Will cause indicators to change colors • A metal + an acid will produce hydrogengas • Single replacement reaction • Acid + metal → hydrogen gas + a“salt” • Double replacement reaction • Acid + Base → water + a“salt” Unit 11 – Acids and BasesNotes #1: Intro

  4. Single replacement reaction • Acid + Metal → __Hydrogen gas_ + a “_salt_” • Double replacement reaction • Acid + Base → _water__ + a “_salt_”

  5. Base: Something that produces a hydroxide ion (OH-) in solution Unit 11 – Acids and BasesNotes #1: Intro

  6. Properties of Bases: • bitter • slippery (soap) • electrolytic • Both strong and weak • Will cause an indicator to change colors Unit 11 – Acids and Bases

  7. Section 20.3 – Other definitions of Acids and Bases • Arrhenius Acids and Bases: • Acid: • Hydrogen containing compound that ionize to yield a hydrogen ion in solution. • Base: • Compounds that ionize to yield a hydroxide ion in solution.

  8. Brønsted – Lowry Acids and Bases • They felt the Arrhenius definition was too limiting. • Acids: • Hydrogen ion donor (Proton donor) • Bases: • Hydrogen ion acceptor (Proton acceptor)

  9. Brønsted – Lowry Acids and Bases • Examples: • NH3 + H2O↔ NH4+ + OH- • H2O donated the H+ - Acid • NH3 accepted the H+ - Base • HCl + H2O ↔ H3O+ + Cl- • HCl donated the H+ - Acid • H2O accepted the H+ - Base

  10. Amphoteric: • Substance that can act as both an acid or a base. • Background Theory: • The oxides of metals are basic in nature. For example, the oxides of the alkali metals (Group I) form alkali or basic solutions. • Sodium oxide + water → Sodium hydroxide solution Na2O(s) + H2O(l) → NaOH(aq) • The soluble oxides of non-metals are acidic in nature. Examples include, carbon dioxide, sulfur dioxide and nitrogen dioxide. • Sulfur dioxide + water → Sulfurous acid SO2(g) + H2O(l) → H2SO3(aq) • Insoluble non-metallic oxides like carbon monoxide do not form acidic solutions. This is often the cause of acid rain. • Compounds such as the amino acids, which contain both acidic and basic groups in their molecules, can also be described as amphoteric.

  11. Strong Acids and Bases • Strong Acids/Bases: • Those that ionize completely in solution. • Ex: HCl, NaOH • Weak Acids/Bases: • Those that only slightly ionize in solution. • Ex: NH3, Acetic Acid (vinegar) • Tooth decay is caused by the weak acid – lactic acid: C3H6O3

  12. Your homework: Page #5 due tomorrow!! Unit 11 – Acids and BasesNotes #1: Intro

  13. Acid/Base Nomenclature • Binary acids are made up of __Hydrogen_ + ___an anion_. • Example: HCl of HF • The pattern for naming Binary Acids is: • Prefix: Hydro- • anion name • Suffix: -ic • Ends with the word “_acid__”.

  14. Examples of Naming Binary Acids • HCl • HF • HBr Hydrochloric acid Hydrofluoric acid Hydrobromic acid

  15. Ternary Acids • These acids contain a ____polyatomic ion___. • Also known as __ternary acids____. • Rules for Naming Ternary Acids • Name the __ polyatomic ion_____. • Change ions ending in • -_ate__ to - _ic__. • Examples: sulfate sulfuric • phosphate phosphoric

  16. Ternary acids cont. • Change ions ending in • -__ite__ to - __ous___. • Examples: sulfitesulfurous • phosphite phosphorous • All end with the word “_acid_”.

  17. Examples of Naming Ternary Acids • H2SO4 • H2CO3 • H2NO2 • H2PO3 Sulfate is the poly, so sulfuric acid carbonate is the poly, so carbonic acid Nitrite is the poly, so nitrous acid phosphite is the poly, so phophorous acid

  18. Remembering Acid Naming Rules w/ Polyatomics “Handle acids carefully so you don’t get a case of “ate-ic-ite-ous.”” • Polys ending in “-ate” are changed to “-ic” • Polys ending in “-ite” are charged to “-ous” Hydro- prefix is not used with poly containing acids!!!!!

  19. Unit 11 – Acids and BasesNotes #1: Intro • Hydrogen with a polyatomicion that ends in -ate • Change suffix to -ic • HNO3 – Nitric Acid • H2SO4 – Sulfuric Acid • Remember …. Acids are sour, so “’-ic, I ate something gross!”

  20. Naming Bases • The easiest are the bases, since most of these are _metalhydroxides, compounds you already know how to name. • Metal hydroxides are named in the same way any other ionic compound is named. First give the name of the _metal_ ion. Follow this with the name of the anion, which, in the case of bases, is “__hydroxide__”. • KOH – • Mg(OH)2 – • Potassium Hydroxide • Magnesium Hydroxide

  21. Name the following acids: • 1. H2S Hydrosulfuric acid • 2. HClO3 Chloric acid • 3. HBrO3Bromic acid • 4. HCN Cyanic acid • 5. H2CrO4 Chromic acid • 6. HNO3Nitric acid • Note: HNO2 Nitrous acid Write the formula for the following acids (follow the same rules as your ionic compounds) 7. Hydroiodic acid HI 8. Hydroselenic acid H2Se 9. Permanganic acid HMnO4 10. Acetic acid HC2H3O2 11. Sulfurous acid H2SO4 In Class Practice for Nomenclature of Acids

  22. Homework: pg 8

  23. The pH Scalepg 9-10

  24. pH Scale

  25. MEASURING pH Scientists use a pH scale to measure the strength of an acid or base. The term pH stands for “potential for hydrogen”. The amount of hydrogen in a substance determines its acidity or alkalinity. Alkaline is another term for base. A number on the pH scale is used to describe the strength of acidity or alkalinity. The most commonly used pH scale goes from 1 (very acidic) to 14 ( very basic). The number 7 on a pH scale means neutral – neither acid nor base. Acids play important roles in the chemistry of living things. Many of the foods you eat are acids in vitamins like ascorbic acid or vitamin C, and folic acid. Other acids help the body such as stomach acids and others are waste products of cell processes like lactic acid in working muscles. Acids also are used to make valuable products for homes, farms and industries. People often use dilute solutions of acids to clean brick and other surfaces. Hardware stores sell muriatic (hydrochloric ) acid, which is used to clean bricks and metals. Industry uses sulfuric acid in car batteries, to refine petroleum and to treat iron and steel. Farmers depend on the nitric acid and phosphoric acid to make fertilizers for crops, lawns, and gardens.

  26. The concentration of hydrogen ions in a solution is described by its number on the pH scale. A low pH tells you that the concentration of hydrogen ion is high. By comparison, a high pH tells you that the concentration of hydrogen ion is low.

  27. Self-ionization of water • Self-ionization of water: • Reaction in which 2 water molecules produce ions • H2O + H2O → OH- + H3O+ • Also written as: • H2O ↔ H+ + OH- • The H3O+ and H+ represent hydrogen ions in solution.

  28. Neutral Solutions • In pure water, the concentration of hydrogen ions is equal to the concentration of hydroxide ions • 1 x 10-7M • Remember M represents Molarity • [H+] = [OH-] • (brackets represent concentration) • This represents a neutral solution.

  29. Concentration of H+ • The concentration of hydrogen ions in a solution is described by its number on the pH scale. • A low pH tells you that the concentration of hydrogen ion is high. By comparison, a high pH tells you that the concentration of hydrogen ion is low.

  30. Solutions • In a solution, if the [H+] increases, the [OH-] decreases and vice versa. • Think back to a see-saw. As one person went up the other went down. • Ion-product constant of water, Kw: • Kw = [H+] x [OH-] = 1 x 10-14M • Acidic Solution: • The [H+] will be greater than the [OH-]. • Therefore, the [H+] is greater than 1 x 10-7M. • Think about the # line. -5 is GREATER than -7 • Basic Solution: • The [H+] will be less than [OH-]. • Therefore, the [H+] is less than 1 x 10-7M. • A.k.a. alkaline solutions

  31. NUMBER LINE and pH • Remember the number line • Which is greater? 0 or 3 • 3 • Which is greater? -7 or -4 • -4 • Which is less? -2 or -4 • -4 • Increasing • 2 • 3 • 4 • -7 • -6 • -5 • -4 • -3 • -2 • -1 • 0 • 1 • 5 • 6 • 7 • 8

  32. Acids Bases

  33. pH and Concentrationpg 12-13 Question 1: If the pH is 2.3 what is the substance? Question 2: what is the pH for a neutral substance?

  34. pH Scale • The pH scale ranges from 0-14. • 0 = strongly acidic • 7 = neutral • 14 = strongly basic • pH = -log [H+] • What is the pH of a neutral solution? • Log is a function on the calculator

  35. Sample Problems • As long as you have a 1 x 10 to some power, the pH is the exponent. 1. What is the pH of the following concentrations? a. [H+] = 1 x 10-2M b. [H+] = 1 x 10-9M c. [H+] = 1 x 10-5M pH = 2 pH = 9 pH = 5

  36. Sample Problems • If you do not have 1 to the power then you MUST use our formulas. 2. What is the pH of the following? a. [H+] = 2x10-2 • pH = -log(2x10-2) = 1.7 pH b. [H+] = 6x10-9 • pH = -log(6x10-9) = 8.2 pH c. [H+] = 3x10-5 • pH = -log(3x10-5) = 4.5 Ph

  37. Other Formulas and Problems • [H+] + [OH-] = 14 • Kw = [OH-] x [H+] = 1x10-14

  38. Other Formulas and Problems 3. What is the pH of a solution with a [OH-] of 4.0 x 10-11M? • Use Kw to find [H+] then find pH using –log function. Step1: Kw = [OH-] x [H+] = 1x10-14 [H+] = 1x10-14/4x10-11 = 2.5x10-4 M Step 2: pH = -log [H+] pH= -log(2.5x10-4) = 3.6

  39. Flow Chart of pH and pOH • Use the map to help you get from any point A to any point B…

  40. 1. If pH = 5, pOH = • pH + pOH = 14 5+ pOH = 14 pOH = 9 Solution is basic

  41. 1. What is the pH of a solution that has a hydrogen ion concentration of 1.0 x 10-5M? Is this solution acidic, basic or neutral? Given: [H+] Solving for: pH pH = - log [H+] pH = - log(1.0 x 10-5 M) pH = 5 pH < 7 ACIDIC

  42. 2. What is the hydrogen ion concentration of a solution with a pH of 11? Which has a greater concentration: H+ or OH-? Given: pH Solving for: [H+] pH > 7 BASIC [OH-] > [H+]

  43. 3. What is the pH of a solution that has a hydrogen ion concentration of 1.2 x 10-8M? Is this solution acidic, basic or neutral? Given: [H+] Solving for: pH pH = - log [H+] pH = - log(1.2 x 10-8 M) pH = 7.92 pH > 7 BASIC

  44. 4) A solution has a hydrogen ion concentration of 1.2x10-8M. Determine the pH of the solution. Is this solution acidic, basic or neutral? Given: [H+] Solving for: pH pH = -log [H+] pH = -log 1.2 x10 -8 = 7.9 Basic solution

  45. 5. Assuming Kw = 1x10-14, calculate the molarity of OH- in solutions at 25ºC when the H+ concentration is 0.2M At 25ºC, Kw = [OH-] [H+] = 1x10-14 [OH-] = 1x10-14 M/ .2 M = 5x10-14 M

  46. Now you try….Homework • Your homework is to do Page 14

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