Acids

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Acids Bases

• Acids
• acids are sour tasting
• Arrhenius acid Any substance that, when
  dissolved in water, increases the concentration
  of hydronium ion (H3O)
• Bronsted-Lowry acid A proton donor
• Lewis acid An electron acceptor
• Bases
• bases are bitter tasting and slippery
• Arrhenius base Any substance that, when
  dissolved in water, increases the concentration
  of hydroxide ion (OH-)
• Bronsted-Lowery base A proton acceptor
• Lewis acid An electron donor

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Lone Hydrogen ions do not exist by themselves in
solution. H is always bound to a water molecule
to form a hydronium ion
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Brønsted-Lowry Theory of Acids Bases Conjugate
Acid-Base Pairs
General Equation
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Brønsted-Lowry Theory of Acids Bases
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Brønsted-Lowry Theory of Acids Bases
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Brønsted-Lowry Theory of Acids Bases
Notice that water is both an acid a base
amphoteric
Reversible reaction
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ELECTROLYTES

• Electrolytes are species which conducts
  electricity when dissolved in water. Acids,
  Bases, and Salts are all electrolytes.
• Salts and strong Acids or Bases form Strong
  Electrolytes. Salt and strong acids (and bases)
  are fully dissociated therefore all of the ions
  present are available to conduct electricity.
• HCl(s) H2O ? H3O Cl-
• Weak Acids and Weak Bases for Weak Electrolytes.
  Weaks electrolytes are partially dissociated
  therefore not all species in solution are ions,
  some of the molecular form is present. Weak
  electrolytes have less ions avalible to conduct
  electricity.
• NH3 H2O ? NH4 OH-

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Acids Bases

• STRONG vs WEAK
• _ completely ionized _ partially ionized
• _ strong electrolyte _ weak electrolyte
• _ ionic/very polar bonds _ some covalent bonds
• Strong Acids Strong Bases
• HClO4 LiOH
• H2SO4 NaOH
• HI KOH
• HBr Ca(OH)2
• HCl Sr(OH)2
• HNO3 Ba(OH)2

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Acids Bases

• One ionizable proton
• HCl ? H Cl-
• Two ionizable protons
• H2SO4 ? H HSO4-
• HSO4- ? H SO42-
• Three ionizable protons
• H3PO4 ? H H2PO4
• H2PO4- ? H HPO42-
• HPO42- ? H PO4-3

Combined H2SO4 ? 2H SO42-
Combined H3PO4 ? 3H PO43-
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Acids Bases

• For the following identify the acid and the base
  as strong or weak .
• a. Al(OH)3 HCl ?
• b. Ba(OH)2 HC2H3O2 ?
• c. KOH H2SO4 ?
• d. NH3 H2O ?

Weak base
Strong acid
Weak acid
Strong base
Strong acid
Strong base
Weak acid
Weak base
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Acids Bases

• For the following predict the product. To check
  your answer left click on the mouse. Draw a
  mechanism detailing the proton movement.
• a. Al(OH)3 HCl ?
• b. Ba(OH)2 HC2H3O2 ?
• c. KOH H2SO4 ?
• d. NH3 H2O ?

AlCl3 3 H2O
3
2
Ba(C2H3O2)2 2 H2O
K2SO4 2 H2O
2
NH4 OH-
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Conjugate Acid-Base Pairs
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Conjugate Acid-Base Pairs
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Acids Bases

• For the following Identify the conjugate acid and
  the conjugate base. The conjugate refers to the
  acid or base produced in an acid/base reaction.
  The acid reactant produces its conjugate base
  (CB).
• a. Al(OH)3 3 HCl ? AlCl3 3 H2O
• b. Ba(OH)2 2 HC2H3O2 ? Ba(C2H3O2)2 2 H2O
• c. 2 KOH H2SO4 ? K2SO4 2 H2O
• d. NH3 H2O ? NH4 OH-

CB CA
CB CA
CB CA
CA CB
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TITRATION

• Titration of a strong acid with a strong base
• ENDPOINT POINT OF NEUTRALIZATION EQUIVALENCE
  POINT
• At the end point for the titration of a strong
  acid with a strong base, the moles of acid (H)
  equals the moles of base (OH-) to produce the
  neutral species water (H2O). If the mole ratio
  in the balanced chemical equation is 11 then the
  following equation can be used.
• MOLES OF ACID MOLES OF BASE
• nacid nbase
• Since Mn/V
• MAVA MBVB

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TITRATION

• MAVA MBVB
• 1. Suppose 75.00 mL of hydrochloric acid was
  required to neutralize 22.50 mLof 0.52 M NaOH.
  What is the molarity of the acid?
• HCl NaOH ? H2O NaCl
• Ma Va Mb Vb rearranges to Ma Mb Vb / Va
• so Ma (0.52 M) (22.50 mL) / (75.00 mL)
• 0.16 M
• Now you try
• 2. If 37.12 mL of 0.843 M HNO3 neutralized
  40.50 mL of KOH, what is the molarity of the base?

Mb 0.773 mol/L
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Molarity and Titration
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TITRATION

• Titration of a strong acid with a strong base
• ENDPOINT POINT OF NEUTRALIZATION EQUIVALENCE
  POINT
• At the end point for the titration of a strong
  acid with a strong base, the moles of acid (H)
  equals the moles of base (OH-) to produce the
  neutral species water (H2O). If the mole ratio
  in the balanced chemical equation is NOT 11 then
  you must rely on the mole relationship and handle
  the problem like any other stoichiometry problem.
  
• MOLES OF ACID MOLES OF BASE
• nacid nbase

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TITRATION

• 1. If 37.12 mL of 0.543 M LiOH neutralized
  40.50 mL of H2SO4, what is the molarity of the
  acid?
• 2 LiOH H2SO4 ? Li2SO4 2 H2O
• First calculate the moles of base
• 0.03712 L LiOH (0.543 mol/1 L) 0.0202 mol LiOH
• Next calculate the moles of acid
• 0.0202 mol LiOH (1 mol H2SO4 / 2 mol LiOH)
  0.0101 mol H2SO4
• Last calculate the Molarity
• Ma n/V 0.010 mol H2SO4 / 0.4050 L
  0.248 M
• 2. If 20.42 mL of Ba(OH)2 solution was used to
  titrate29.26 mL of 0.430 M HCl, what is the
  molarity of the barium hydroxide solution?

Mb 0.308 mol/L
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Molarity and Titration

• A student finds that 23.54 mL of a 0.122 M NaOH
  solution is required to titrate a 30.00-mL sample
  of hydr acid solution. What is the molarity of
  the acid?
• A student finds that 37.80 mL of a 0.4052 M
  NaHCO3 solution is required to titrate a 20.00-mL
  sample of sulfuric acid solution. What is the
  molarity of the acid?
• The reaction equation is
• H2SO4 2 NaHCO3 ? Na2SO4 2 H2O 2 CO2

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Water Equilibrium
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Water Equilibrium

• Kw H OH- 1.0 x 10-14
• Equilibrium constant for water

• Water or water solutions in which H OH-
  10-7 M are neutral solutions.
• A solution in which H gt OH- is acidic
• A solution in which H lt OH- is basic

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pHA measure of the hydronium ion

• The scale for measuring the hydronium ion
  concentration H3O in any solution must be able
  to cover a large range. A logarithmic scale
  covers factors of 10. The p in pH stands for
  log.
• A solution with a pH of 1 has H3O of 0.1
  mol/L or 10-1
• A solution with a pH of 3 has H3O of 0.001
  mol/L or 10-3
• A solution with a pH of 7 has H3O of
  0.0000001 mol/L or 10-7
• pH - log H3O

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The pH scale

• The pH scale ranges from 1 to 10-14 mol/L or from
  1 to 14.
• pH - log H3O
• 1 2 3 4 5 6 7 8 9 10 11 12 13
  14
• acid neutral base

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Manipulating pH

• Algebraic manipulation of
• pH - log H3O
• allows for
• H3O 10-pH
• If pH is a measure of the hydronium ion
  concentration then the same equations could be
  used to describe the hydroxide (base)
  concentration.
• OH- 10-pOH pOH - log OH-
• thus
• pH pOH 14 the entire pH range!

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PRACTICE PROBLEM 25

• 1. How many milliliters of 1.25 M LiOH must be
  added to neutralize 34.7 mL of 0.389 M HNO3?
• 2. What mass of Sr(OH)2 will be required to
  neutralize 19.54 mL of 0.00850 M HBr solution?
• 3. How many mL of 0.998 M H2SO4 must be added to
  neutralize 47.9 mL of 1.233 M KOH?
• 4. What is the molar concentration of hydronium
  ion in a solution of pH 8.25?
• 5. What is the pH of a solution that has a molar
  concentration of hydronium ion of 9.15 x 10-5?
• 6. What is the pOH of a solution that has a molar
  concentration of hydronium ion of 8.55 x 10-10?

10.8 mL
0.0101 g
29.6 mL
5.623 x 10-9 M
pH 4.0
pOH 4.9
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GROUP STUDY PROBLEM 25

• ______1. How many milliliters of 0.75 M KOH must
  be added to neutralize 50.0 mL of 2.50 M HCl?
• ______2. What mass of Ca(OH)2 will be required
  to neutralize 100 mL of 0.170 M HCl solution?
• ______3. How many mL of 0.554 M H2SO4 must be
  added to neutralize 25.0 mL of 0.9855 M NaOH?
• ______ 4. What is the molar concentration of
  hydronium ion in a solution of pH 2.45?
• ______ 5. What is the pH of a solution that has a
  molar concentration of hydronium ion of 3.75 x
  10-9?
• ______ 6. What is the pOH of a solution that has
  a molar concentration of hydronium ion of 4.99 x
  10-4?