Chapter 15 Acids bases

acids• Sour• Turns litmus red• Reacts with some metals to

produce H2

• Phenolphthalein-clear• Corrosive• Conducts electricity

bases• Bitter• Turns litmus blue• Slippery

• Phenolphthalein-pink• Corrosive• Conducts electricity

Arrhenius Acid

• produces hydronium ions (H3O+) hydrogen ions (H+) in water

• dissociate• HCl(g) -----> H+(aq) + Cl-(aq) • HCl(g) + H2O(l) -----> H3O+(aq) + Cl-(aq)

• HF(g) + H2O(l) -----> H3O+(aq) + F-(aq)

• H2SO4(aq) + H2O(l) --------> H3O+(aq) + HSO4- (aq)

Electrolytes dissociate into ions

• Strong electrolyte –completely dissociates

• K eq is large-lots of ions• Weak electrolyte

partially dissociates• K eq is small, not many

ions

• Strong acid –completely dissociates

• Ka is large-lots of ions• Weak acid• partially dissociates• Ka is small, not many

ions• Ka =ionization constant

Strong Acids [H3O+]

• HCl• HNO3

• H2SO4

• HBr• HI

• What is the hydronium ion [H3O+] concentration in a .10 M HCl solution?

• HCl(g) + H2O(l) -----> H3O+(aq) + Cl-(aq)

Weak Acids [H3O+]

• What is the hydronium ion concentration in a .10 M HF solution? (Ka =6.8 x 10-4)

• HF(g) + H2O(l) <-----> H3O+(aq) + F -(aq)

Find Ka for weak acid• A .10 M weak acid has a hydronium ion concentration of 3.0 x 10 -4 M? What is the Ka? (ionization constant)

Arrhenius Base• produces hydroxide (OH-) ion in water• NaOH(s) -----> Na+(aq) + OH-(aq)

• Strong base-completely dissociates Kb is large-favors products• Weak base-partially dissociates Kb is small-favors reactants

Strong Bases

• NaOH• LiOH• KOH• RbOH• CsOH• Ca(OH)2

• Sr(OH)2

• Ba(OH)2

• What is the hydroxide ion concentration in a .10 M NaOH solution?

Weak Base

• NH3 is a weak base

• NH3(g) + H2O(l) <-----> NH4+(aq) + OH-(aq)

• What is the hydroxide ion concentration in a 0.10 M NH3 solution? (Kb for NH3 is 1.8 x 10 -5)

Neutralization• HCl(aq) + NaOH(aq) -------> H2O(l) + NaCl (aq)• Acid + Base water + a salt• H+ (aq) + OH- (aq)-------> H2O (l) • H3O+ (aq) + OH- (aq)------->2 H2O (l) • Titration process of adding an acid to a base or base to an acid• Equivalence point -moles of H3O+ (H+) = moles of OH-

• Indicator changes color at a certain [H3O+]• End point when color changes• When titrating to neutrality End point and equivalence point

should be very close (Choose an indicator that changes color when moles of H+ = moles of OH-)

• When neutralizing a strong acid with strong base the indicator phenolphthalein is usually used

Titration molarity of an acid or base

orvolume of an acid or base

• What volume of .10 M HCl is needed to neutralize 10. mL of .20 M NaOH?

• One to one ratio use MaVa=MbVb• Not one to one ratio use stoichiometry

• What volume of .10 M HCl is needed to neutralize 10. mL of .30 M Ca(OH)2?

• What is the molarity of an HCl solution if it takes 5.0 mL of .20 M NaOH solution to neutralize 8.0 mL of the HCl?

• What is the molarity of an H2SO4 solution if it takes 5.0 mL of .20 M NaOH solution to neutralize 4.0 mL of the HCl?

Bronsted-Lowry acids and basesdoes not need to be in water

Bronsted Acid• Proton (H+) donor• strong acid –readily

donates a proton- large Ka• weak acid – does not

readily donate a proton- small Ka

Bronsted Base• Proton (H+) acceptor• strong base –readily

accepts a proton- large Kb• weak base – does not

readily accept a proton- small Kb

• HCl (aq) + H2O (l) <------> H3O+ (aq) + Cl- (aq)

• NH3 (aq) + H2O(l)< -----> NH4+ (aq) + OH-(aq)

Conjugate acid/base pair

• To find conjugate base-remove H+ (proton)

• Acid conjugate base• HF• HC2H3O2

• HSO4-

• To find conjugate acid-add H+ (proton)

• Base conjugate acid• OH- • NH3

• CO32-

• H2O(l) + H2O(l) <-----> H3O+(aq) + OH- (aq)• Keq = Kw = 1.0 x 10 -14

• 1.0 x 10 -14 = [H3O+] [OH-]

• Pure water [H3O+] = [OH-]

1.0 x 10 -14 = [H3O+] [OH-]

• What is the hydronium ion concentration if the hydroxide ion concentration of a solution is 1.0 x 10 -2?

• What is the hydroxide ion concentration if the hydronium ion concentration of a solution is 2.0 x 10 -4?

• Acid - more hydronium ions than hydroxide ions

• Base - more –hydroxide ions than hydronium ions

pH = –log[H3O+]

• Log in base 10 • number to which 10 must

be raised to equal that number

• Log of .10 = ?• .10 = 10 -1

• log = -1

• Log of .010 = ?• .010 = 10 -2

• log = -2

• What is the pH of a solution that has a hydronium in concentration of .10 M?

• pH =1• What is the pH of a solution

that has a hydronium in concentration of .010 M?

• pH =2

hydronium hydroxide pH Acid/base 0.100 0.01 1.0 X 10 -7

1.0 x 10 -12

1.0 x 10 -9

What is the pH of a solution if the hydronium ion concentration is 2.5 x 10 -3 M ?

• Estimate

• On calculator enter -log[H3O+] =

Given pH find hydronium ion concentration

• pH = 1 hydronium ion concentration = .10 M or 10-1 M• pH = 2 = = .010 M or 10-2 M• pH = 9 = 10-9 M• pH = 12 10-12 M• What is the hydronium ion concentration of a solution that

has a pH of 4.8?• On calculator enter 10 x (2nd log button) - pH

pH scale• 0_________________________________ 7_____________________________________14• acid neutral base (alkaline)

• H3O+ > OH- OH- > H3O+

• The lower the pH the more acidic The higher the pH the more basic