Chemistry: Arrhenius Theory & Mass Action Law
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Questions and Answers

What is the concentration of H+ ions in pure water?

  • 10-9 mole
  • 10-8 mole
  • 10-7 mole (correct)
  • 10-6 mole

    • What does a larger K₂ value indicate about an acid?

  • Weaker acid
  • Stronger base
  • Neutral strength
  • Stronger acid (correct)

    • If the pH of a solution is less than 7, what can be inferred about the solution?

  • It is acidic (correct)
  • It is neutral
  • It is alkaline
  • It has a higher concentration of OH- ions

    • How is the relationship between pKa and acid strength characterized?

    <p>Higher pKa indicates weaker acid</p> Signup and view all the answers

    What is the formula to calculate pOH from pH?

    <p>pOH = 14 - pH</p> Signup and view all the answers

    When the concentration of H+ ions is greater than 10-7, how is the solution classified?

    <p>Acidic</p> Signup and view all the answers

    What does an increase in Ka imply about an acid?

    <p>It is strengthening</p> Signup and view all the answers

    Which statement is true about pH and pKa?

    <p>pH measures ion concentration; pKa measures dissociation strength</p> Signup and view all the answers

    Which substances are classified as non-electrolytes?

    <p>Alcohols and glucose</p> Signup and view all the answers

    For a strong electrolyte, the degree of dissociation (α) is approximately equal to which value?

    <p>1</p> Signup and view all the answers

    What does the degree of dissociation (α) indicate?

    <p>The extent to which electrolyte molecules split into ions</p> Signup and view all the answers

    What is the dissociation equation for hydrochloric acid (HCl) in water?

    <p>HCl → H+ + Cl-</p> Signup and view all the answers

    According to the law of mass action, which equation defines the equilibrium constant (K)?

    <p>K = [C][D] / [A][B]</p> Signup and view all the answers

    Which of the following statements is true regarding the dissociation of water?

    <p>Water ionizes to a very small extent.</p> Signup and view all the answers

    What does the symbol K represent in the context of chemical reactions?

    <p>Equilibrium constant</p> Signup and view all the answers

    If the degree of dissociation (α) is 60%, what does this imply?

    <p>60% of the molecules have dissociated into ions.</p> Signup and view all the answers

    What is the pH of a completely ionized 1.0 N solution of hydrochloric acid?

    <p>0</p> Signup and view all the answers

    For a solution of 0.009 N hydrochloric acid, what is the pH?

    <p>2.05</p> Signup and view all the answers

    How is the pH of a weak acid, like acetic acid, calculated?

    <p>pH = ½ (pKa + pCa)</p> Signup and view all the answers

    What would be the pH of a 0.0045 M solution of phenobarbital with a pK of 7.41?

    <p>4.88</p> Signup and view all the answers

    Calculate the pH of a 0.13 N ammonia solution with a pK of 4.76.

    <p>11.18</p> Signup and view all the answers

    What is the hydroxyl ion concentration of a solution with a pH of 10.75?

    <p>5.62 x 10^-4 M</p> Signup and view all the answers

    If the pH of a solution is 5.3, what is the hydrogen ion concentration?

    <p>5.01 x 10^-6 M</p> Signup and view all the answers

    A salt formed from a strong acid and a strong base typically has what pH?

    <p>pH = 7</p> Signup and view all the answers

    What is hydrolysis in the context of salts?

    <p>The reaction of an ion with water to produce conjugate acids and bases.</p> Signup and view all the answers

    Which condition results in a salt solution having a pH less than 7?

    <p>Salt derived from a strong acid and a weak base.</p> Signup and view all the answers

    In the context of ammonia chloride (NH4Cl), which statement is correct regarding its hydrolysis?

    <p>It results in the generation of H+ ions, leading to an acidic solution.</p> Signup and view all the answers

    What determines the pH level of a salt solution?

    <p>The strengths of the acids and bases from which the salt is derived.</p> Signup and view all the answers

    How do you calculate the percentage of salt hydrolyzed in solution?

    <p>100 x (y/Cs)</p> Signup and view all the answers

    Given a 0.1 M sodium acetate solution with a pK of 4.76, what is the calculated pH?

    <p>8.88</p> Signup and view all the answers

    In the context of salts, what is the degree of hydrolysis?

    <p>The fraction of total salt that undergoes hydrolysis at equilibrium.</p> Signup and view all the answers

    What is the expected pH for a salt formed from a weak acid and a weak base?

    <p>pH is indeterminate without more information.</p> Signup and view all the answers

    Study Notes

    Arrhenius Theory of Ionization/Dissociation

    • Electrolytes dissociate into oppositely charged ions when dissolved in water.
    • Non-electrolytes do not ionize at all in solution.
    • Degree of Dissociation (α): The fraction of molecules that dissociate into ions; expressed as a percentage.
      • α = (number of molecules dissociated / total number of molecules) x 100%
    • Strong Electrolytes (Strong acids and bases) have α close to 1.
    • Weak Electrolytes (Weak acids and bases) have α less than 1.

    Law of Mass Action

    • The rate of a chemical reaction is proportional to the active masses of the reacting substances.
    • Equilibrium Constant (K): Ratio of product concentrations to reactant concentrations at equilibrium.
      • K = [C][D] / [A][B]
    • Dissociation of Water:
      • Water is a weak electrolyte, H₂O ↔ H+ + OH-
      • Ionic Product of Water (Kw): [H+][OH-] = 10⁻¹⁴
      • pH Scale:
        • pH = -log[H⁺], pOH = -log[OH⁻]
        • pKw = pH + pOH = 14
        • Neutral:[H+] = [OH-] = 10⁻⁷
        • Acidic: [H+] > 10⁻⁷
        • Alkaline (Basic): [H+] < 10⁻⁷

    Dissociation of Acids and Bases

    • Weak Acids: HA + HOH <=> H3O+ + A-
      • Ka: Acid ionization constant, K = [H+][A-] / [HA]
    • Weak Bases: B + HOH <=> BH+ + OH-
      • Kb: Base ionization constant, K = [BH+][OH-] / [B]
    • pKa and pKb: Relate to the strength of acids and bases:
      • pKa = -logKa, pKb = -logKb
      • Larger Ka (smaller pKa) = Stronger acid
      • Larger Kb (smaller pKb) = Stronger base

    Importance of Dissociation Constants

    • Ka and Kb values determine the strength of acids and bases.
    • pH Calculations:
      • Strong Acid: pH = -log [H+], pH = pC₂ (concentration of acid)
      • Strong Base: pH = pKw - pCb (concentration of base)
      • Weak Acid: pH = ½ (pKa + pCa)
      • Weak Base: pH = pKw - ½ (pKb + pCb)
    • Salts:
      • Neutral Salt: Formed by the reaction of a strong acid and a strong base, pH = 7.
      • Basic Salt: Formed by the reaction of a weak acid and a strong base, pH > 7.
      • Acidic Salt: Formed by the reaction of a strong acid and a weak base, pH < 7.
      • Salt of Weak Acid & Weak Base: pH = 0.5 (pKa + pKb - pCs)
    • Degree of Hydrolysis (h): The fraction of salt hydrolyzed at equilibrium.
      • h = (concentration of hydrolyzed species) / (concentration of salt)
      • % hydrolysis = 100 x h
    • Remember:*
    • pKa gives information about the acid's dissociation in water; pH gives information about the H+ concentration in solution.
    • The stronger the acid or base, the higher the Ka or Kb values, and the lower the pKa or pKb values.
    • The pH of a salt solution depends on the strengths of the original acid and base that formed it.

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    Description

    This quiz covers essential concepts from the Arrhenius Theory of Ionization/Dissociation and the Law of Mass Action. Learn about electrolytes, the degree of dissociation, and the equilibrium constant. Test your knowledge on these fundamental principles of chemistry.

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