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Acids/Bases/ch 15

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Acids/Bases/ch 15. Acid/base. Electrolyte—any substance which will form ions in solution and conduct electricity Three classes of electrolytes: A) Acids B) Bases C) Salts. Acid/Base. Properties of Acids: A) taste sour B) turn litmus red C) clear in phenolphthalein

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acid base
Acid/base
  • Electrolyte—any substance which will form ions in solution and conduct electricity
  • Three classes of electrolytes:
  • A) Acids
  • B) Bases
  • C) Salts
acid base1
Acid/Base
  • Properties of Acids:
  • A) taste sour
  • B) turn litmus red
  • C) clear in phenolphthalein
  • D) react with water to form H3O+
  • E) react with metals to form H2 gas
acid base2
Acid/Base
  • Strong acids—dissociate in water to form many ions “go to completion”. Have high Ka
  • Ex: HCl(aq) + H2O  H3O+(aq) + Cl-(aq)
  • Only 6 strong acids exist:
  • HCl HBr HI HNO3
  • HClO4 H2SO4
  • Show the dissociation on the board for each.
acid base3
Acid/Base
  • Monoprotic acids---acids with only one hydrogen to ionize
  • HCl, HBr, HI, HF, HNO3, HClO4,CH3COOH
acid base4
Acid/Base
  • Diprotic acids—those with 2 “H” to ionize
  • H2SO4 and H2CO3
acid and base
Acid and Base
  • Triprotic Acids—those with 3 “H” to ionize
  • H3PO4

Polyprotic acids---those with more than one “H” to ionize

acid base5
Acid/Base
  • Binary acids---those with only two elements
  • Ternary acids—those with “3” elements
acid base6
Acid --Base
  • Weak acids---- those which do NOT dissociate completely in water/
  • Equilibrium is reached ()
  • HF(aq) + H2O  H3O+(aq) + F-(aq)
  • Or
  • CH3COOH(aq) + H2O  H3O+(aq) + CH3COO-(aq)
acid base7
Acid/Base
  • Properties of Bases:
  • A) taste bitter
  • B) turn litmus blue
  • C) turn pink in phenolpthalein
  • D) release OH- in solution
  • E) feel slippery to the touch
  • F) forms alkaline solutions
acid base8
Acid -base
  • Strong bases---dissociate completely in water
  • Strong bases are: bases with cations from groups 1 or 2
  • ex: NaOH, KOH, LiOH, Ca(OH)2, Mg(OH)2
acid base9
Acid/Base
  • Ex:
  • NaOH(aq) Na+(aq) + OH-(aq)
  • Ca(OH)2(aq)  Ca+2(aq) + 2OH-(aq)
  • ********note that when strong bases dissociate all OH- are released
acid base10
Acid/Base
  • Weak bases—dissociate only a small amount and few ions form. Equilibrium is reached ()
  • NH4OH(aq)  NH4+(aq) + OH-(aq)

or

Al(OH)3(aq)  Al+3(aq) + 3OH-(aq)

acid base11
Acid/Base
  • Neutralization: (double replacement)
  • Acid + base => water + salt
  • HCl + KOH => HOH + KCl
  • Write the balanced equation for?
  • Sulfuric acid reacts with calcium hydroxide
acid base12
Acid/Base
  • Acids will always form the hydronium ion
  • (H3O+) when put into water.
  • Draw the structural formula on board
  • Structural formula shows bonding and where each atom is located in the molecule.
acid base13
Acid/Base
  • Three classes of Acids and Bases:
  • A) Arrhenius
  • B) Bronsted-Lowry
  • C) Lewis
acid base14
Acid/Base
  • Arrhenius:
    • Acid: releases H+ into solution (HBr, HCl, etc)
    • Base: releases OH- into solution (KOH, NaOH,etc)
acid base15
Acid/Base
  • Bronsted-Lowry:
  • Acid: a proton donor
  • Base: a proton acceptor
  • HCl(aq) + H2O  H3O+(aq) + Cl-(aq)
  • (Cl-) is the spectator ion ( does NOT participate in reaction)
acid base16
Acid/Base
  • H2SO4(aq) + H2O => H3O+(aq) + HSO4-(aq)
  • What is the spectator ion?
acid base17
Acid -Base
  • Conjugate base: of an acid is the part that remains after a proton has been released
  • (always a product)
  • HF + H2O => H3O+ + F-
  • F- is the conjugate base
  • Demo on the board
acid base18
Acid- Base
  • Conjugate acid- of a base is formed when the base accepts the proton from the acid
  • ( always a product)
  • H3O+ is the conjugate acid of the previous reaction

H2SO4 + H2O => H3O+ + HSO4-

acid base c. acid c. base

acid base19
Acid/Base
  • A B
  • HI _____
  • CH3COOH ______
  • H3O+ _______
  • ______ OH-
  • ______ HSO4-
acid base20
Acid-Base
  • Lewis :
  • acid: an e- pair acceptor
  • base: an e- pair donor
  • BF3 + NH3 => F3BNH3
  • Demo on board
acid base21
Acid/Base
  • Amphoteric: substance which acts as an acid or a base ex: water
  • Demo on board
  • hydrochloric acid + water =>
  • ammonia + water =>
acid base22
Acid/Base
  • Anhydrous: Without water
  • Acidic anhydride---an oxide that will produce an acid when added to water
  • carbon dioxide + water => carbonic acid
  • Basic anhydride—an oxide that will produce a base when added to water
  • sodium oxide + water => sodium hydroxide
ph scale
pH Scale
  • Acid or base ?
  • pH scale is from 0-14
  • less than 7 ----acid
  • Greater than 7---basic
  • pH 7 ---neutral
  • Pure water is neutral
ph scale1
pH Scale
  • Acid /base indicators can be used to determine if a solution is an acid or a base. Acid base
  • Litmus red blue
  • Phenolphthalein clear pink
  • Phenol red yellow green
  • Different indicators will work at different pH levels
acid base23
Acid/Base
  • Phenolphthalein works best between 8.5 and 10.
  • Could you use Phenolphthalein on a solution with pH 6.5 ? Why? Why not?
acid base24
Acid/Base
  • Pure water will ionize only a small amount.
  • ( it will be at equilibrium)
  • HOH(l) H+(aq) + OH-(eq)
  • K(eq) = [H+][OH-]
  • Since it takes 107 liters of water to form 1 mole of hydroxide ion and 1 mole of hydrogen ion, its Molarity is 1Mol/107liters
  • M = 1 X 10-7 for each ion
acid base25
Acid/Base
  • The special equilibrium for water is :
  • Kw = [H+][OH-]
  • Kw = [ 1x 10-7][ 1 x 10-7]
  • Kw = 1 X 10 -14
  • Kwalways = 1 x10-14
  • ******note H+ is the same as H3O+
acid base26
Acid – Base
  • [H+] = [OH-] in pure water
  • If you know the [ ] of the H+ you can calculate the [ ] of the OH- and vice versa
acid base27
Acid-base
  • Ex: What is the [OH-] in a solution of .25M hydrochloric acid .
  • Step one: determine if acid is strong
  • Step two: write hydrogen ion concentration in exponential form
  • Step three: use Kw to solve the problem
  • Kw = [H+][OH-]
  • 1 x 10-14 = [ 2.5 x 10-1] [ OH-]
  • [OH-] = 1 X 10-14/ 2.5 X 10-1
  • [OH-] = 4 X 10 -14
acid base28
Acid - Base
  • Demo on the board
  • Page 541 (1-4)
slide36
pH
  • pH can be calculated from the [H+]
  • pH = -log[H+]
  • Ex: What is the pH of a solution with:
  • [H3O+] = 1 X 10-3
  • pH = -log(1 X 10-3)
  • pH = -1(-3)
  • pH = 3
  • Demo on calculator
slide37
pOH
  • pOH = -log [OH-]
  • What is the pOH of a solution that is .0001 M sodium hydroxide?
  • Sodium hydroxide is a strong base so it ionizes completely.
  • [OH-] = 1 X 10 -4
  • pOH = -log ( 1 X 10-4)
  • pOH = -1(-4)
  • pOH = 4
ph and poh
pH and pOH
  • pH + pOH = 14
slide39
pH

Calculate the pH of the following:

a) [H+] = 3.0 X 10-8

b) [OH-] = 4.0 X 10-6

c) [H3O+] = 8.2 X 10-6

Determine for each example if it is acid, base, or neutral.

slide40
pH
  • True or false:
  • As the [H3O+] increases the pH increases.
  • As the solution becomes more basic the [OH-] increases
  • As the pH increases the [OH-] increases
  • In pure water [H+] = [OH-]
titrations
Titrations
  • Acid-base titration—process in which a neutralization reaction is used to determine the concentration of a solution with unknown molarity.
titrations1
Titrations
  • An acid base indicator showing the color change at the “end point” will be used.
  • End point—point in the titration in which the color of the solution changes
  • Equivalence point---the point at which the amount of acid will neutralize the base. Mols of [H+] = mols of [OH-]
titration
Titration
  • Titration curves:
  • Strong acid titrated with strong base (p551)
  • Weak acid titrated with strong base
  • Strong acid titrated with weak base
  • Plateau of each curve represents the part of the titration in which the hydrogen ion is neutralizing the hydroxide ion.
titrations2
Titrations
  • Solving titration problems:
  • VaMa = VbMb

What is the molarity of a NaOH solution if 40.0 ml of the solution is neutralized by 35.6 ml of .24 M solution of HBr.

VaMa = VbMb

35.6 ml x .24 M = 40.0ml X Mb

Mb = .21 M

slide47

Buffer solutions: solutions which resist changes in pH

  • Blood needs to have pH from 7.35 to 7.45.
  • If below 7.35 you suffer acidosis
  • If above 7.45 you suffer alkalosis
slide48

Acidosis: blood overwhelmed with too much acid ( leg cramps after exhausting excerise)

  • Alkalosis: blood has too little acid. ( hyperventilation ---body loses too much CO2)
slide49

Buffer solution : is made from a WEAK acid and its conjugate base. This will neutralize the change in pH.

  • If the solution is “buffered” the addition of a small amount of acid or base will NOT change the pH
salts
Salts
  • Salt—an ionic compound composed of the cation of the base and the anion of the acid. May be soluble or insoluble.
  • Old book page 920---table

ex: sulfuric acid reacts with calcium hydroxide.

  • Write the balanced equation
  • Classify the reaction
  • Name the salt
  • Determine if the salt is soluble or insoluble
salts1
Salts
  • Aluminum hydroxide reacts with nitric acid.
  • Write the balanced equation
  • Name the salt
  • Is the salt insoluble or soluble
review
Review
  • Pp 566-567
  • # 1-2
  • #4-9
  • #11
  • #14-19
  • # 25
  • #29
  • #40-45
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