CHAPTER 9 CONCURRENT ENROLLMENT

ACIDS AND BASES WEAK ACIDS AND BASES ONLY A FEW IONS ARE FORMED DEFINITIONS –Arrhenius - Acid contains H + ions and Bases contain OH - ions –Bronsted - Acid donates H + ions and Bases accept H + ions –Lewis - Acid an electron pair acceptor and Bases an electron pair donator WEAK ACIDS AND BASES ONLY A FEW IONS ARE FORMED DEFINITIONS –Arrhenius - Acid contains H + ions and Bases contain OH - ions –Bronsted - Acid donates H + ions and Bases accept H + ions –Lewis - Acid an electron pair acceptor and Bases an electron pair donator

ELECTROLYTES SOLUTE (usually salt) placed in a SOLVENT (usually water) the solution will conduct electricity –Strong electrolytes - –Weak electrolytes - NONELECTROLYTES –Do not conduct electricity IONIZATION –Molecular compounds have covalent bonds broken and ions are made DISSOCIATION –Ionic compounds are attracted to the polar water molecule and become free floating ions SOLUTE (usually salt) placed in a SOLVENT (usually water) the solution will conduct electricity –Strong electrolytes - –Weak electrolytes - NONELECTROLYTES –Do not conduct electricity IONIZATION –Molecular compounds have covalent bonds broken and ions are made DISSOCIATION –Ionic compounds are attracted to the polar water molecule and become free floating ions

CONJUGATE ACID-BASE PAIRS NH 3 (g) + H 2 O(l) -> NH 4 + (aq) + OH - (aq) Base Acid Conjugate Conjugate Acid Base STRENGTHS –A weak acid will have a strong conjugate base –When a reaction is transferring protons it favors making a weak acid and base AMPHOTERIC –Can be an acid or base NH 3 (g) + H 2 O(l) -> NH 4 + (aq) + OH - (aq) Base Acid Conjugate Conjugate Acid Base STRENGTHS –A weak acid will have a strong conjugate base –When a reaction is transferring protons it favors making a weak acid and base AMPHOTERIC –Can be an acid or base

SELF-IONIZATION H 2 O(l) + H 2 O(l) OH - (aq) + H 3 O + (aq) Neutral –When the concentrations of H 3 O + and OH - are equal. –A water solution with a pH of 7 K w = [OH - ][H 3 O + ] Acidic solution has more H 3 O + than OH - ions so the solution has a pH less than 7 Basic solution has more OH - than H 3 O + ions so the solution has a pH greater than 7 Learning check page 274 H 2 O(l) + H 2 O(l) OH - (aq) + H 3 O + (aq) Neutral –When the concentrations of H 3 O + and OH - are equal. –A water solution with a pH of 7 K w = [OH - ][H 3 O + ] Acidic solution has more H 3 O + than OH - ions so the solution has a pH less than 7 Basic solution has more OH - than H 3 O + ions so the solution has a pH greater than 7 Learning check page 274

THE pH SCALE Concentration of H 3 O + ions [H + ] pH = -log[H 3 O + ] K w = [H 3 O + ][OH - ] [H 3 O + ] = 10 -pH 1 X = [H 3 O + ][OH - ] pH + pOH = 14 Concentration of H 3 O + ions [H + ] pH = -log[H 3 O + ] K w = [H 3 O + ][OH - ] [H 3 O + ] = 10 -pH 1 X = [H 3 O + ][OH - ] pH + pOH = 14

ACID Any substance that donates H + ions TASTE - TOUCH - Reacts with METALS to form hydrogen gas Strong acids conduct ELECTRICITY (100% ionization) A COLOR change occurs when an indicator comes in contact with an acid When mixed with a base it is neutralized, forming a water STRONG ACIDS - HCl, H 2 SO 4 (dilute), HNO 3, HClO 4, HClO 3, HBr, HI WEAK ACIDS - H 3 PO 4, HF, any acid containing carbon, carboxyl group --COOH Any substance that donates H + ions TASTE - TOUCH - Reacts with METALS to form hydrogen gas Strong acids conduct ELECTRICITY (100% ionization) A COLOR change occurs when an indicator comes in contact with an acid When mixed with a base it is neutralized, forming a water STRONG ACIDS - HCl, H 2 SO 4 (dilute), HNO 3, HClO 4, HClO 3, HBr, HI WEAK ACIDS - H 3 PO 4, HF, any acid containing carbon, carboxyl group --COOH

Acid reactions 2HCl(aq) + CuO(s) CuCl 2 (aq) + H 2 O(l) Copper oxide 2HCl(aq) + Ca(OH) 2 (s) CaCl 2 (aq) + 2H 2 O(l) Calcium hydroxide 2HCl(aq) + CaCO 3 (s) CaCl 2 (aq) + CO 2 (g) + H 2 O(l) Calcium carbonate 2HCl(aq) + Sr(HCO 3 ) 2 (s) CaCl 2 (aq) + 2CO 2 + 2H 2 O(l) Strontium bicarbonate ACID-BASE NEUTRALIZATION HCl(aq) + NaOH(aq) -----> H 2 O(l) + NaCl(aq) Strong Strong Water Soluble Acid Base Salt 2HCl(aq) + CuO(s) CuCl 2 (aq) + H 2 O(l) Copper oxide 2HCl(aq) + Ca(OH) 2 (s) CaCl 2 (aq) + 2H 2 O(l) Calcium hydroxide 2HCl(aq) + CaCO 3 (s) CaCl 2 (aq) + CO 2 (g) + H 2 O(l) Calcium carbonate 2HCl(aq) + Sr(HCO 3 ) 2 (s) CaCl 2 (aq) + 2CO 2 + 2H 2 O(l) Strontium bicarbonate ACID-BASE NEUTRALIZATION HCl(aq) + NaOH(aq) -----> H 2 O(l) + NaCl(aq) Strong Strong Water Soluble Acid Base Salt

SALTS Activity series for metals page 280 SALTS –Ionic compounds where the metal (cation) ion comes from a base and the nonmetal (anion) ion comes from an acid –If a salt contains a CATION from a STRONG BASE and a ANION from a WEAK ACID it will be basic -Na 2 CO 3 (BASIC pH >7) –NaCl - Strong base and strong acid (NEUTRAL about 7) –MgCl 2 - Strong acid and weak base (ACIDIC pH <7) –MgCO 3 - Weak acid and weak base (DEPENDS) on which solution has a greater # of hydrogen ions Hydrate - salt that contains a certain number of water molecules as part of the solid crystalline structure Activity series for metals page 280 SALTS –Ionic compounds where the metal (cation) ion comes from a base and the nonmetal (anion) ion comes from an acid –If a salt contains a CATION from a STRONG BASE and a ANION from a WEAK ACID it will be basic -Na 2 CO 3 (BASIC pH >7) –NaCl - Strong base and strong acid (NEUTRAL about 7) –MgCl 2 - Strong acid and weak base (ACIDIC pH <7) –MgCO 3 - Weak acid and weak base (DEPENDS) on which solution has a greater # of hydrogen ions Hydrate - salt that contains a certain number of water molecules as part of the solid crystalline structure

BASE ANY SUBSTANCE THAT ACCEPTS H + IONS TASTE - TOUCH - STRONG BASES - Group one metals, Barium, Strontium with OH - forming a compound WEAK BASES - NH 3, other nitrogen containing compounds (amines --NH 2 ) and other OH - compounds Equivalents page ANY SUBSTANCE THAT ACCEPTS H + IONS TASTE - TOUCH - STRONG BASES - Group one metals, Barium, Strontium with OH - forming a compound WEAK BASES - NH 3, other nitrogen containing compounds (amines --NH 2 ) and other OH - compounds Equivalents page

ACID CONSTANT HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq) K a = [H 3 O + ][A - ] [HA] Constant for weak acids and bases p. 286 B(aq) + H 2 O(l) OH - (aq) + HB + (aq) K b = [OH - ][HB + ] [B] Monoprotic acid –One hydrogen ion removed from acid Diprotic acid –Two hydrogen ions removed from acid Triprotic acid –Three hydrogen ions removed from acid HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq) K a = [H 3 O + ][A - ] [HA] Constant for weak acids and bases p. 286 B(aq) + H 2 O(l) OH - (aq) + HB + (aq) K b = [OH - ][HB + ] [B] Monoprotic acid –One hydrogen ion removed from acid Diprotic acid –Two hydrogen ions removed from acid Triprotic acid –Three hydrogen ions removed from acid

INDICATOR, BUFFERS, AND TITRATIONS Indicator –Indicators are optical compounds, in the presence of an acid the shape will be different than with a base, color change Buffers –Weak acid or base and the common anion salt, helps to resist change in pH –Blood is a natural buffer. If pH changes from 7.35 to 7.45 the body would shut down and you could die –Buffer capacity - the amount of acid (H + ) or base (OH - ) that can be absorbed by a buffer without causing a significant change in pH Titrations –By adding a known concentration to an unknown concentration (containing an indicator) until a color change occurs Indicator –Indicators are optical compounds, in the presence of an acid the shape will be different than with a base, color change Buffers –Weak acid or base and the common anion salt, helps to resist change in pH –Blood is a natural buffer. If pH changes from 7.35 to 7.45 the body would shut down and you could die –Buffer capacity - the amount of acid (H + ) or base (OH - ) that can be absorbed by a buffer without causing a significant change in pH Titrations –By adding a known concentration to an unknown concentration (containing an indicator) until a color change occurs

HYDROLYSIS AND HENDERSON- HASSELBALCH EQUATION A reaction with water. For salts it is a reaction of the acidic cation and/or basic anion of the salt with water Page 295 A relationship between the pH of a buffer, pK a, and the concentrations of acid and salt in the buffer pH = pK a + log [B - ] [HB] pH = -log[H + ] and pK a = -log K a Pages A reaction with water. For salts it is a reaction of the acidic cation and/or basic anion of the salt with water Page 295 A relationship between the pH of a buffer, pK a, and the concentrations of acid and salt in the buffer pH = pK a + log [B - ] [HB] pH = -log[H + ] and pK a = -log K a Pages