BELLWORK- pH calcs

Determine the pH of the following solutions.

a)   [H+] = 5.2x10-9 M (estimate)
b)   [OH-] = 4.9x10-4 ...
19.3- Weak vs. Strong
Lemons and grapefruits
have a sour taste because
they contain citric acid.
Sulfuric acid is a widely...
Strong acids and bases
 completely dissociate
Strong acids and bases
   completely dissociate


   AT EQUILIBRIUM

HCl + H2O  Cl- + H3O+
little      lots lots
Weak acids and bases
only partly dissociate.
Weak acids and bases
       only partly dissociate.
When in water most of the weak acid
 will keep its proton attached.
Weak acids and bases
        only partly dissociate.
When in water most of the weak acid
 will keep its proton attached.
A...
Weak acids and bases
        only partly dissociate.
When in water most of the weak acid
 will keep its proton attached.
A...
Which acid will produce more H+,
   1M HCl or 1M acetic acid?
Which acid will produce more H+,
   1M HCl or 1M acetic acid?


          HCl is strong!
          HC2H3COO is weak
Recognize the name, formula, and relative strength (weak
  or strong) of the following:
           Memorize thisWEAK ACIDS...
• A strong acid has a weak conjugate base.
• A weak acid has a strong conjugate base.

• A strong base has a weak conjugat...
Predict the products and label the
 conjugate acid-base pairs as weak or
 strong.

NH3 + HCl  _______ + _______

CH3COOH ...
An acid dissociation constant (Ka)
describes the equilibrium between an
acid and the ions it forms.


          HA       H...
Weak acids have small Ka values.
The stronger an acid is, the larger is
its Ka value.
The base dissociation constant (Kb)
describes the equilibrium of a base.


               [HB +][OH-]
         Kb = ------...
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Lecture 19.3- Weak vs. Strong PREP

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Lecture 19.3 for Prep Chemistry

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Lecture 19.3- Weak vs. Strong PREP

  1. 1. BELLWORK- pH calcs Determine the pH of the following solutions. a) [H+] = 5.2x10-9 M (estimate) b) [OH-] = 4.9x10-4 M (estimate) c) pOH = 5.7 d) 0.01M HNO3 e) 0.10M NaOH
  2. 2. 19.3- Weak vs. Strong Lemons and grapefruits have a sour taste because they contain citric acid. Sulfuric acid is a widely used industrial chemical that can quickly cause severe burns if it comes into contact with skin. You will learn why some acids are weak and some acids are strong.
  3. 3. Strong acids and bases completely dissociate
  4. 4. Strong acids and bases completely dissociate AT EQUILIBRIUM HCl + H2O  Cl- + H3O+ little lots lots
  5. 5. Weak acids and bases only partly dissociate.
  6. 6. Weak acids and bases only partly dissociate. When in water most of the weak acid will keep its proton attached.
  7. 7. Weak acids and bases only partly dissociate. When in water most of the weak acid will keep its proton attached. Acetic acid(vinegar) is a weak acid.
  8. 8. Weak acids and bases only partly dissociate. When in water most of the weak acid will keep its proton attached. Acetic acid(vinegar) is a weak acid. AT EQUILIBRIUM CH3COOH + H2O  CH3COO- + H3O+ lots little little
  9. 9. Which acid will produce more H+, 1M HCl or 1M acetic acid?
  10. 10. Which acid will produce more H+, 1M HCl or 1M acetic acid? HCl is strong! HC2H3COO is weak
  11. 11. Recognize the name, formula, and relative strength (weak or strong) of the following: Memorize thisWEAK ACIDS STRONG ACIDS HCl hydrochloric acid CH3COOH H2SO4 sulfuric acid aka HC2H3O2 or HNO3 nitric acid acetic acid (vinegar) STRONG BASES WEAK BASES NaOH sodium hydroxide NH3 ammonia Bronsted-Lowry! KOH potassium hydroxide Arrhenius!
  12. 12. • A strong acid has a weak conjugate base. • A weak acid has a strong conjugate base. • A strong base has a weak conjugate acid. • A weak base has a strong conjugate acid.
  13. 13. Predict the products and label the conjugate acid-base pairs as weak or strong. NH3 + HCl  _______ + _______ CH3COOH + NH3  _______ + _______
  14. 14. An acid dissociation constant (Ka) describes the equilibrium between an acid and the ions it forms. HA H+ + A-
  15. 15. Weak acids have small Ka values. The stronger an acid is, the larger is its Ka value.
  16. 16. The base dissociation constant (Kb) describes the equilibrium of a base. [HB +][OH-] Kb = ---------------- [B] The larger the Kb the more dissociation occurs, so the stronger the base.

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