The Chemistry of Acids and Bases

Acids pH below 7 turns litmus paper red taste sour reacts with metals to produce H2(g) generally starts with a hydrogen ion [H+] > [OH-] HCl

generally contains a hydroxide ion Bases pH greater than 7 turns litmus paper blue taste bitter feel slippery generally contains a hydroxide ion [H+] < [OH-] NaOH

contains H+ and OH- ions Both Acids and Bases amphoteric an electrolyte contains H+ and OH- ions

Acidic, Basic, and Neutral Solutions Type of Solution pH Ranges [H+] versus [OH-] Example Acidic Below 7 [H+] > [OH-] Orange Juice Battery Acid Your Stomach Neutral Equals EXACTLY 7 [H+] = [OH-] Distilled Water Basic Above 7 [H+] < [OH-] Bleach Sea Water Blood

Indicators Indicators are compounds that have one color in acidic solutions and another in basic.

Litmus Paper Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Paper or plastic strips that contain combinations of indicators estimate the pH of a solution by simply dipping a piece of pH paper into it and comparing the resulting color with standards printed on the container Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Range and Color Changes of Some Common Acid-Base Indicators pH Scale 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Indicators Methyl orange red 3.1 – 4.4 yellow Methyl red red 4.4 6.2 yellow Bromthymol blue yellow 6.2 7.6 blue Neutral red red 6.8 8.0 yellow From F. Brescia et al., Chemistry: A Modern Introduction, W. B. Saunders Co., 1978. Adapted from R. Bates, Determination of pH, Theory and Practice, John Wiley & Sons, Inc., New York, 1964. Choosing the correct indicator for an acid-base titration 1. For titrations of strong acids and strong bases (and vice versa), any indicator with a pKin between 4 and 10 will do 2. For the titration of a weak acid, the pH at the equivalence point is greater than 7, and an indicator such as phenolphthalein or thymol blue, with pKin > 7, should be used 3. For the titration of a weak base, where the pH at the equivalence point is less than 7, an indicator such as methyl red or bromcresol blue, with pKin < 7, should be used Phenolphthalein colorless 8.0 10.0 red colorless beyond 13.0 Bromthymol blue indicator would be used in titrating a strong acid with a strong base. Phenolpthalein indicator would be used in titrating a weak acid with a strong base. Methyl orange indicator would be used in titrating a strong acid with a weak base.

pH Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.

Naming Acids Naming Binary Acids 1. Name begins with prefix hydro- 2. Root of second element follows hydro and ends with the suffix -ic

BINARY ACIDS HBr (aq) Hydrobromic Acid

BINARY ACIDS HCl (aq) Hydrochloric Acid

BINARY ACIDS HI (aq) Hydroiodic Acid

Examples of BINARY ACIDS Hydrofluoric acid HF Hydrochloric acid HCl Hydrobromic acid HBr Hydrosulfuric acid H2S

-ous polyatomic ending -ic -ate -ite Nitrate Naming Ternary Acids H + polyatomic ion Begin with ion without the Add suffix if there was an Add suffix if there was an HNO3  polyatomic ending -ic -ate -ous -ite Nitrate “In the cafeteria, you ATE something ICky” Nitric acid

Naming Ternary Acids TERNARY ACIDS SO42- H2SO4 H2SO4(aq) Sulfuric acid POLYATOMIC IONS PURE FORMS TERNARY ACIDS SO42- H2SO4 H2SO4(aq) Sulfuric acid SO32- H2SO3 H2SO3(aq) Sulfurous Acid

TERNARY ACIDS Naming Ternary Acids PO43- H3PO4 H3PO4(aq) POLYATOMIC IONS PURE FORMS TERNARY ACIDS PO43- H3PO4 H3PO4(aq) Phosphoric acid PO33- H3PO3 H3PO3(aq) Phosphorus Acid

Acid Nomenclature Flowchart

Naming Bases polyatomic Sodium hydroxide Calcium hydroxide Use the same rules as for ions (name the cation, then name the anion) NaOH  Ca(OH)2  KOH  Sodium hydroxide Calcium hydroxide Potassium hydroxide

Naming Bases NaOH Sodium Hydroxide

Naming Bases MgOH Magnesium Hydroxide

Naming Bases KOH Potassium Hydroxide

Common Bases Lye, Drano Potash Cleaners Baking soda Tums /Rolaids Milk of Magnesia Baking soda Tums /Rolaids Limestone, shells Soaps Detergents NaOH KOH NH3 or NH4OH Mg(OH)2 NaHCO3 CaCO3 NaC16O2H31 NaC12O4H25S Sodium Hydroxide Potassium Hydroxide Ammonia Magnesium Hydroxide Sodium Bicarbonate Calcium Carbonate Sodium Palmitate Sodium Lauryl Sulfate

Common Acids Battery Acid Stomach Acid Coca Cola Carbonated Water H2SO4 HCl H3PO4 H2CO3 HC2H3O2 H3C6O7H8 HC6O6H7 H2C4O6H4 H2C9O4H8 Battery Acid Stomach Acid Coca Cola Carbonated Water Vinegar Citrus fruits Vitamin C Grapes Aspirin Sulfuric Acid Hydrochloric Acid Phosphoric Acid Carbonic Acid Acetic Acid Citric Acid Ascorbic Acid Tartaric Acid Acetyl Salicylic Acid

Definitions for Acids & Bases   Arrhenius Brønsted-Lowry Definition for Acids Definition for Bases Key Examples a proton producer in an aqueous solution a proton donor a hydroxide producer in an aqueous solution a proton acceptor Acid – HCl Base - NaOH Acid – HCl Base – NH3 H+ = proton

What to Focus On? Arrhenius was the most restrictive definition. This definition required:   the solutions to be aqueous and a base to contain a hydroxide (OH-) ion. Bronsted-Lowry’s definition is the most commonly used. It is helpful to remember: acids tend to “lose“ an H+ ion, while bases tend to “gain“ an H+ ion. Under this definition, ammonia (NH3) is considered a base even though it is NOT an Arrhenius base.

Examples HCl(aq) + KOH(s) H2O(l) + KCl(aq)   3 Ca(OH)2(aq) + 2 H3PO4(aq)  Ca3(PO4)2(s) + H2O(l) F-(aq) + H2O(l)  HF(aq) + OH-(aq) HCO3-(aq) + H2O(l)  CO32-(aq) + H3O+(aq) NH4+(aq) + CO32-(aq)  NH3(aq) + HCO3-(aq) acid base base acid base acid acid base acid base

Remember Electrolytes? Ionic Covalent C6H12O6 Na+ NaCl Cl-

Acids and bases are both strong or weak electrolytes (conduct electricity) • Electrolytes = dissociate (break apart into ions) when dissolved • Strong = completely Weak = partially Non = not at all Weak Strong H+ HC2H3O2 C2H3O21- H+ H-Cl Cl- Only a few Ions Lots of Ions

Strong Electrolytes PICTURE WORD DESCRIPTION Completely breaks apart into its ions Are good conductors of electricity Will produce a bright light bulb Examples of Acids and Bases that are Strong Electrolytes Strong Acids Strong Bases H2SO4 NaOH HCl Ba(OH)2 Notice that all of the ions are separated or dissociated. = positive ions = negative ions The title is hyperlinked to a NCSSM animation of HCl dissolving in water.

Weak Electrolytes WORD DESCRIPTION Partially breaks apart into its ions Are poor conductors of electricity Will produce a dim light bulb Examples of Acids and Bases that are Weak Electrolytes Weak Acid HC2H3O2 (Vinegar) Weak Base NH3 (Ammonia) Notice that only some of the ions are separated or dissociated. PICTURE = positive ions = negative ions The title is hyperlinked to a NCSSM animation showing HA (a weak acid) dissolving in water.

What makes a strong acid or a strong base? Strong electrolytes make strong acids and bases Strong Acids HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric acid HBr - hydrobromic acid HI - hydroiodic acid HClO4 - perchloric acid Strong Bases The hydroxides of the Group I and Group II LiOH - lithium hydroxide NaOH - sodium hydroxide KOH - potassium hydroxide *Ca(OH)2 - calcium hydroxide *Sr(OH)2 - strontium hydroxide *Ba(OH)2 - barium hydroxide The title is hyperlinked to a NCSSM animation of HCl dissolving in water.

pH Concept

pH Scale Pouvoir hydrogéne (hydrogen power) Range is 0-14 Acids 0-7 Bases 7-14 Neutral = 7.0

Relationships between pH, [H+], and [OH-] Click on the picture to get to the animation. As pH increases… The [H+] (increases or decreases). The [OH-] (increases or decreases). The solution becomes more (acidic or basic).

Relationships between pH, [H+], and [OH-] What happens as pH decreases? As pH decreases… The [H+] (increases or decreases). The [OH-] (increases or decreases). The solution becomes more (acidic or basic).

The pH Scale The value of pH is unitless. Solutions with a pH less than 7 are acidic and solutions greater than 7 are basic. If a solution is equal to 7 it is neutral. Here is a typical pH scale.

pH of Common Substances

pH Calculations Given Solving for Formula to Use [H+] pH pH = - log[H+] [OH-] pOH pOH = - log[OH-] [H+] is the concentration of H+ ions, in mol/L.

Logarithms Use your calculator! If you have a log button, you’re all set. Each calculator can have its own method for entering logs. If you don’t know what to do your calculator manual should give examples. 1.44939 E -2 9 - 43

Logarithms If your calculator has a ln button - Don’t use it. Its for taking natural logs. This is different than base 10. 1.44939 E -2 9 - 44

Calculating pH If [H+] is written in scientific notation and has a coefficient of 1, then the pH of the solution equals the absolute value of the exponent Ex. 1.0 x 10-4 M pH = 4.0

Calculating pH Problem 1: If [H+] = 3.40 x 10-5 M, what is the pH? Given Unknown Equation [H+] = 3.40 x 10-5 M pH pH = - log[H+] Solve: pH = -log (3.40 x 10-5) pH = 4.47

Calculating pH Problem 2: If [H+] = 1 X 10-10, what is the pH? Given Unknown Equation [H+] = 1 X 10-10 pH pH = - log[H+] Solve: pH = - log 1 X 10-10 pH = - (- 10) pH = 10

Calculating pH Problem 3: If [H+] = 1.8 X 10-5, what is the pH? Given Unknown Equation [H+] = 1.8 X 10-5 pH pH = - log[H+] Solve: pH = - log 1.8 X 10-5 pH = - (- 4.74) pH = 4.74

Calculating pOH Solve: Problem 1: pOH = -log (2.3 x 10-12) pOH = 11.6 If [OH-] = 2.30 x 10-12 M, what is the pOH? Given Unknown Equation [OH-] = 2.30 x 10-12 M pOH pOH = - log[OH-] Solve: pOH = -log (2.3 x 10-12) pOH = 11.6

Calculating pOH If [OH-] is written in scientific notation and has a coefficient of 1, then the pOH of the solution equals the absolute value of the exponent Problem 2: If [OH-] = 1.0 x 10-9 M, what is the pH? pOH = 9.0

What’s in a glass of water? distilled

Distilled H2O at the Molecular Level What’s in a glass of distilled water? Water Molecules (H2O) Hydronium Ions (H3O+) Hydroxide Ions (OH-) What’s happens in the glass of water? H2O + H2O ⇆ H3O+ + OH- This is called the self-ionization of water.

pH + pOH = 14 Water Water ionizes- falls apart into ions. H2O ® H+ + OH-. Only a small amount. [H+ ] = [OH-] = 1 x 10-7M A neutral solution. In water Kw = [H+ ] x [OH-] = 1 x 10-14 Kw is called the ion product constant. pH + pOH = 14 Amphoteric a molecule or ion that can react as an acid as well as a base Ex: H2O, NH3

Calculating pOH from pH Problem 1: If the pH is 3.25, what is the pOH? Given pH = 3.25 Unknown pOH ? Equation pH + pOH = 14 Substitute and solve : 3.25 + pOH = 14 3.25 + (- 3.25) +pOH = 14 (- 3.25) pOH = 10.8

Calculating pH from pOH Problem 2: What is the pH of a solution if [OH-] = 4.0 x 10-11 M? Given [OH-] = 4.0 x 10-11 M Unknown pH? Equation pH + pOH = 14 Step 1: Find pOH pOH = -log [OH] pOH= -log[4.0 x 10-11 ] = 10.4 Step 2: Calculate pH pH + pOH= 14; pH = 14 – 10.4 pH = 3.6

Looking at the Math Given Solving for Formula to Use pH [H+] pOH [OH-]

Calculating [H+] from pH If the pH of Coke is 3.12, [H+] = ??? [ H+] = 10-3.12 = 7.6 x 10-4 M *** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button Known pH = 3.12 Unknown [H+] ? Analysis [H+] = 10 -pH Substitute and solve :

Calculating [H+] from pH The pH of an unknown solution is 6.00. What is its [H+]? Known pH = 6.00 Unknown [H+] ? Analysis [H+] = 10 -pH Substitute and solve : [H+] = 1x 10 -6 M

Calculating [H+] from pH A solution has a pH of 8.5. What is the Molarity of hydrogen ions in the solution? Known pH = 8.5 Unknown [H+] ? Analysis [H+] = 10 -pH Substitute and solve : [H+] = 10-8.5 3.16 X 10-9 M

Types of Chemical Reactions Solution Reactions are classified as follows: Precipitation reactions When two solutions are mixed, an insoluble solid forms B. Acid-Base reactions A soluble hydroxide and a soluble acid react to form water and a salt C. Oxidation-Reduction reactions (redox rxns) Reactions in which one or more electrons are transferred

A. Precipitation Reactions When two solutions are mixed, an insoluble substance (solid) sometimes forms and separates from the solution. Such a reaction is called a precipitation reaction, and the solid that forms is called a precipitate. Example: K2CrO4(aq) + Ba(NO3)2(aq)  KNO3 (aq) + BaCrO4 (s) (Soluble) (Soluble) (Soluble) (Precipitate) * Double replacement reactions

A. Precipitation Reactions Mixing KI (aq) and Pb(NO3)2 (aq) leading to precipitation of PbI2

B. Acid-Base Reactions or Neutralization Reactions acid + base  water + salt HBr(aq) + NaOH(aq)  H2SO4(aq) + KOH(aq)  H3PO4(aq) + Ba(OH)2(aq)  H2O + NaBr H2O + K2SO4 H2O + Ba3(PO4)2 * Double replacement reactions

C. Oxidation-Reduction Reactions In oxidation-reduction (redox) reaction, one species loses electrons while another species gains electrons.

C. Oxidation-Reduction Reactions Oxidation Numbers The concept of oxidation numbers is a simple way of keeping track of electrons in a reaction. The oxidation number (or oxidation state) of an atom in a substance is the actual charge of the atom. It is hypothetical charge assigned to the atom in the substance by simple rules.

C. Oxidation-Reduction Reactions

C. Oxidation-Reduction Reactions Loss of 2 e-1 oxidation Gain of 2 e-1 reduction * NOT Double replacement reactions

Types of Reactions Tips Always ends with a salt and water Check to see if one of the product is insoluble in water and look for (s) solid product Look for transitional metals that are able to change their oxidation number

Types of Reactions The reaction of HNO3 (aq) + KOH(aq) → KNO3 (aq) + H2 O(l) is best classified as a(n) a) acid-base neutralization reaction b) oxidation-reduction reaction c) precipitation reaction *

Na3 PO4 (aq) + 3 AgNO3 (aq) → Ag 3PO4 (s) + 3 NaNO3 (aq) Types of Reactions The reaction of Na3 PO4 (aq) + 3 AgNO3 (aq) → Ag 3PO4 (s) + 3 NaNO3 (aq) is best classified as a(n) a) acid-base neutralization reaction b) oxidation-reduction reaction c) precipitation reaction *

Types of Reactions The reaction of is best classified as a(n) C2 H12 O6 (s) + 6 O2 (g) → 6 CO2 (g) + 6 H2O(l) is best classified as a(n) a) acid-base neutralization reaction b) precipitation reaction c) oxidation-reduction reaction *