Chemistry in the Kitchen Unit 3: Acids & Bases pH Reactions with Metals Neutralization Reactions

Electrolytes Ionic Covalent C6H12O6 Na+ NaCl Cl-

Acids Strong Weak HC2H3O2 H-Cl C2H3O21- Cl- H+ H+ Only a few Ions Lots of Ions

Acid = gives hydrogen ions in water Acids Acid = gives hydrogen ions in water HCl H+ + Cl- H+ H-Cl Cl- hydrogen ion

Acid = gives hydrogen ions in water Acids Acid = gives hydrogen ions in water H-Cl + H-O-H Cl- H-Cl + Cl- hydronium ion

Common Acids Strong Weak H2SO4 Battery Acid HCl Stomach Acid H3PO4 H2CO3 HC2H3O2 H3C6O7H8 HC6O6H7 H2C4O6H4 H2C9O4H8 Battery Acid Stomach Acid Coca Cola Carbonated Water Vinegar Citrus fruits Vitamin C Grapes Aspirin Strong 100% ionization Strong electrolyte Weak Partial ionization Weak electrolyte Taste sour

Acids H-Cl + H-O-H + Cl- H-C2H3O2 + H-O-H + C2H3O2- H-Cl HC2H3O2 Cl-

Bases Base = gives hydroxide ions in water. (Arrhenius definition) = takes hydrogen ions in water. (Bronsted-Lowry definition) OH- Na+ NaOH NaOH Na+ + OH-

Common Bases Lye, Drano Potash Cleaners Baking soda Tums /Rolaids Milk of Magnesia Baking soda Tums /Rolaids Limestone, shells Soaps Detergents Amines (Alkaloids) NaOH KOH NH3 or NH4OH Mg(OH)2 NaHCO3 CaCO3 NaC16O2H31 NaC12O4H25S R-NH2 Sodium Hydroxide Potassium Hydroxide Ammonia Magnesium Hydroxide Sodium Bicarbonate Calcium Carbonate Sodium Palmitate Sodium Lauryl Sulfate Caffeine, Nicotine

Common Bases Strong Weak 100% ionization Strong electrolyte Lye, Drano Potash Cleaners Milk of Magnesia Baking soda Tums /Rolaids Limestone, shells Soaps Detergents Amines (Alkaloids) NaOH KOH NH3 or NH4OH Mg(OH)2 NaHCO3 CaCO3 NaC16O2H31 NaC12O4H25S R-NH2 Strong 100% ionization Strong electrolyte Weak Partial ionization Weak electrolyte Taste bitter Feel Slippery

Water is Amphoteric: (Acid or Base) HNO3 HNO3 + H-O-H + NO3- Acid donates an H+ Base takes an H+ Acid Base NH3 Acid donates an H+ Base takes an H+ Base takes an H+ Acid donates an H+

Ionization of Water H2O + H2O HO- + H3O+ Base Acid Acid Base

Ionization of Water H2O + H2O HO- + H3O+ Neutral: if [H3O+] = [OH-] BASE ACID ACID BASE 0.000,000,1M = 1 x 10-7M 0.000,000,1M = 1 x 10-7M Neutral: if [H3O+] = [OH-] Acidic: if [H3O+] > [OH-] Basic: if [H3O+] < [OH-]

pH HCl HC2H3O2 H2O NH3 NaOH -2 Acidic 4 7 Neutral NaHCO3 8 Basic 9 12 = 1 x 10 -pH pH = - log [H+] HCl HC2H3O2 Vinegar H2O NH3 NaOH 100 M = 1 x 10 2 M 0.000,000,1 M = 1 x 10 -7 M -2 Acidic 0.000,1 M = 1 x 10 -4 M 4 7 Neutral NaHCO3 Baking Soda 0.000,000,01 M = 1 x 10 -8 M 8 0.000,000,001 M = 1 x 10 -9 M Basic 9 0.000,000,000,001 M = 1 x 10 -12 M 12

pH HCl HC2H3O2 H2O NaOH -2 Acidic 4 7 Neutral NaHCO3 8 Basic 12 [H+] = 1 x 10 -pH pH = - log [H+] HCl HC2H3O2 vinegar H2O NaOH 100 M = 1 x 10 2 M 0.000,000,1 M = 1 x 10 -7 M -2 Acidic 0.000,76 M = 7.6 x 10 -4 M Citric Acid 0.000,1 M = 1 x 10 -4 M 4 7 Neutral NaHCO3 Baking Soda 0.000,000,01 M = 1 x 10 -8 M 8 Basic 0.000,000,000,001 M = 1 x 10 -12 M 12

pH 3 HC2H3O2 3 - 4 0.000,76 M = 7.6 x 10 -4 M 4 [H+] = 1 x 10 -pH pH = - log [H+] HC2H3O2 0.001 M = 1 x 10 -3 M 3 3 - 4 0.000,76 M = 7.6 x 10 -4 M pH = - log (7.6 x 10 -4) Citric Acid = 3.1 0.000,1 M = 1 x 10 -4 M 4

pH Indicators Pigments: pH meter: pH paper: Litmus paper: Anthocyanins: red cabbage, cranberries, roses… Phenolphthalein: Turmeric:

Anthocyanin Pigments Food source Anthocyanin content in mg per 100 g Açaí 320 Blackcurrant 190-270 Chokeberry 1,480[8] Eggplant 750 Blood orange ~200 Marion blackberry 317[9] Black raspberry 589[10] Raspberry 365 Wild blueberry 558[11] Cherry 350-400 Redcurrant 80-420 Purple corn 1,642[12

Anthocyanin Pigments Food source Anthocyanin content in mg per 100 g Açaí 320 Blackcurrant 190-270 Chokeberry 1,480[8] Eggplant 750 Blood orange ~200 Marion blackberry 317[9] Black raspberry 589[10] Raspberry 365 Wild blueberry 558[11] Cherry 350-400 Redcurrant 80-420 Purple corn 1,642[12 Anthocyanin Pigments

Anthocyanin Pigments

Chlorophyll Color Changes of Chlorophyll in Response to Changes in pH Under more or less neutral conditions, chlorophyll has its normal vegetable green color (think of raw green beans or broccoli) Chlorophyll

Color Changes of Chlorophyll in Response to Changes in pH Under acidic conditions, the magnesium atom (Mg+2) is lost and the color changes to the characteristic pheophytin olive green color. No Mg+2 atom Pheophytin

Color Changes of Chlorophyll in Response to Changes in pH Under alkaline conditions the methyl and phytyl esters are removed, producing chlorophyllin which is a bright green color. No ester groups Chlorophyllin

Color Changes of Chlorophyll in Response to Changes in pH Chlorophyllase Other reactions, mediated by the enzyme chlorophyllase, may result in changes in the pigment, even under conditions of frozen storage. This is why such vegetables (green beans, broccoli, etc.) are blanched (put briefly in boiling water) before preservation by freezing. This destroys the enzyme activity.

Acid Reactions HCl + Zn  ZnCl2 + H2 Acid Metal Salt H+ Cl- Zn

Activity series of metals - various metals in HCl Iron Zinc Magnesium

Activity series of metals potassium sodium calcium magnesium aluminum zinc chromium iron nickel tin lead copper silver platinum gold Reacts violently with cold water Reacts slowly with cold water Reacts very slowly with steam but quite reactive in acid increasing reactivity Reacts moderately with high levels of acid Hydrogen (acid) Unreactive in acid

Carbonated beverages in coated cans Al foil on lazagna Pineapple in tin vs Al Tin coated with plastic Al pop cans coated w plastic Grape juice in glass

Acid-Base Reactions HCl + NaOH  NaCl + HOH Neutralization: Water Acid Salt Neutralization: Strong Acid + Strong Base H+ Cl- Na+ OH-

Acid-Base Reactions 2 2 H2SO4 + KOH  K2SO4 + HOH Water Acid Base Salt

Acid-Base Reactions HC2H3O2 + NaHCO3 Acid Base NaC2H3O2 + H2CO3 Salt Vinegar & Baking Soda HC2H3O2 + NaHCO3 Acid Base NaC2H3O2 + H2CO3 Salt C2H3O21- H+ H2O + CO2(g) Na+ HCO31-

Acid-Base Reactions Cream of Tartar & Baking Soda Acid Rain on Marble HC2H3O2 + NaHCO3 NaC2H3O2 + H2CO3 Acid Base Salt H2O + CO2(g) Acid Rain on Marble H2SO4 + CaCO3 CaSO4 + H2CO3 Acid Base Salt H2O + CO2(g)

Acid-Base Reactions Lemon on Fish H3C6H8O7 + R-NH2 C6H8O71- + R-NH31+ Salt