Study support for Acids and Bases
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What is the hydrogen ion concentration, [H+], of a solution with a pH of 3?

  • 1 x 10^-3 M (correct)
  • 3 x 10^-14 M
  • 3 M
  • 1 x 10^3 M

    • Which of these statements is correct regarding a strong acid?

  • It has a pH value that will always be 7.
  • It dissociates minimally in water.
  • It has a high pKa value.
  • It dissociates completely in water. (correct)

    • What happens to the pH of pure water if the temperature is decreased?

  • The pH will stay exactly at 7.
  • The pH increases making it more basic. (correct)
  • The pH decreases making it more acidic.
  • The pH will approach 0.

    • What is the hydroxide ion concentration, [OH-], if the hydrogen ion concentration is 1 x 10^-2 M in an aqueous solution at 25°C?

    <p>1 x 10^-12 M</p> Signup and view all the answers

    A weak acid is titrated with a strong base, what does the pH at the equivalence point look like?

    <p>pH &gt; 7</p> Signup and view all the answers

    A buffer solution contains a weak acid and its conjugate base, at pH 6. If the pKa of the weak acid is 5, then what can be inferred?

    <p>There is excess conjugate base.</p> Signup and view all the answers

    Which of these conditions gives the greatest buffering capacity?

    <p>Equal concentrations of weak acid and conjugate base.</p> Signup and view all the answers

    How does the electronegativity of an atom bonded to the acidic hydrogen on an acid affect its acid strength?

    <p>More electronegative atoms increase acidity.</p> Signup and view all the answers

    What occurs when a strong acid is combined with a strong base?

    <p>Water is formed and the pH is neutral.</p> Signup and view all the answers

    How does the pH of a buffer solution change when small amounts of a strong acid are added?

    <p>The pH remains relatively stable.</p> Signup and view all the answers

    What defines a weak acid based on its dissociation in solution?

    <p>It partially ionizes.</p> Signup and view all the answers

    What effect does increasing temperature have on the pH of water?

    <p>pH decreases, making it more acidic.</p> Signup and view all the answers

    Which statement is true regarding the equivalence point in a titration involving a weak acid and a strong base?

    <p>The pH at the equivalence point is above 7.</p> Signup and view all the answers

    Which of the following equations correctly represents the relationship between pH and pKa in a buffer solution?

    <p>pH = pKa + log([A-]/[HA])</p> Signup and view all the answers

    How does the ratio of conjugate base to weak acid affect a buffer's capacity?

    <p>Higher ratios increase buffering capacity against acids.</p> Signup and view all the answers

    Which of the following is a characteristic of strong acids and bases?

    <p>They dissociate completely in solution.</p> Signup and view all the answers

    Which factors contribute to the strength of an acid?

    <p>Electronegativity and stability of the conjugate base.</p> Signup and view all the answers

    The pH of pure water is 6 at 25°C.

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

    A strong acid will completely dissociate in solution.

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

    The pKa of a weak acid is directly proportional to its acidity strength.

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

    In a titration of a weak acid with a strong base, the equivalence point occurs at pH 7.

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

    Increasing temperature will cause the pH of a solution to decrease.

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

    Buffers can only consist of strong acids and strong bases.

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

    The Henderson-Hasselbalch equation can be used to calculate the pH of a buffer solution.

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

    All strong bases are derived from Group 1 and Group 2 hydroxides.

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

    Match the following terms with their corresponding definitions:

    <p>pH = a measure of hydrogen ion concentration pOH = a measure of hydroxide ion concentration pKa = a measure of acid dissociation Kw = the ion-product constant for water</p> Signup and view all the answers

    Match the acid/base type with their reaction characteristics,

    <p>Strong acid + strong base = Neutralization to form water Weak acid + strong base = Forms water and conjugate base Weak base + strong acid = Forms conjugate acid Weak acid + weak base = Forms conjugate base and conjugate acid</p> Signup and view all the answers

    Match the following scenarios with the corresponding pH shifts during acid-base titration:

    <p>Strong acid - strong base titration = Equivalence point at pH 7 Weak acid - strong base titration = Equivalence point above pH 7 Weak base - strong acid titration = Equivalence point below pH 7 Halfway to equivalence point of weak acid = pH equals pKa</p> Signup and view all the answers

    Match the following properties of acids or bases with their characteristics:

    <p>Stronger acid = Higher Ka value Stronger acid/weaker base = More electronegative atom bonded to acidic H Stronger base = Less electronegative atom bonded to acidic H Stronger buffer = Greater concentration of weak acid and conjugate base</p> Signup and view all the answers

    Match the conditions with their relation to pH in a buffer system:

    <p>pH = pKa = Equal concentrations of weak acid and conjugate base pH &gt; pKa = More conjugate base than weak acid pH &lt; pKa = More weak acid than conjugate base Buffering capacity maximum = Equal concentrations of weak acid and conjugate base</p> Signup and view all the answers

    Match the following concepts in acid-base chemistry with their description:

    <p>Dissociation = Separation of molecules into ions Equilibrium = Rate of forward reaction equals the rate of reverse reaction Titration = Process to determine the concentration of unknown solution with solution with known concentraton Buffering Capacity = Ability of a solution to resist pH changes</p> Signup and view all the answers

    Match the following mathematical expressions with their application in solution chemistry:

    <p>pH = -log[H+] = Calculating pH from hydrogen ion concentration pOH = -log[OH-] = Calculating pOH from hydroxide ion concentration Kw = [H+][OH-] = Ion-product constant for water pH = pKa + log([A-]/[HA]) = Henderson-Hasselbalch equation</p> Signup and view all the answers

    Match the terms with their relevance in acid-base chemistry:

    <p>Strong acids = Completely dissociate in solution Weak acids = Partially dissociate in solution Buffer solutions = Resist changes in pH upon addition of acid or base Equivalence point = Stoichiometrically equal amount of titrant and analyte are present</p> Signup and view all the answers

    Study Notes

    Introduction to Acids and Bases

    • pH = -log[H+]; pOH = -log[OH-]
    • Kw = [H+][OH-] = 1 x 10-14 at 25°C
    • Pure water has a pH of 7, pOH of 7, and Kw of 1 x 10-14
    • Temperature affects pH:
      • Above 25°C, pH decreases (more acidic)
      • Below 25°C, pH increases (more basic)

    Strong Acids and Bases

    • Strong acids and bases dissociate 100% in solution.
    • Strong acids and bases are strong electrolytes and conduct electricity well.
    • Strong acid examples: HCl, HBr, HI, H2SO4, HNO3, HClO4
    • Strong base examples: Group 1 hydroxides (LiOH, NaOH, KOH) and Group 2 hydroxides (Ba(OH)2, Sr(OH)2)
    • Calculate pH/pOH for strong acids/bases using pH = -log[H+] and pOH = -log[OH-]. pOH + pH = 14

    Weak Acids and Bases and Equilibria

    • Weak acids and bases dissociate only partially in solution.
    • Use Ka or Kb values to determine the strength of a weak acid or base.
    • Ka = [H+][A-]/[HA] (equilibrium constant for weak acid dissociation)
    • pKa = -log Ka
    • Use ICE tables and the Ka or Kb expression to solve equilibrium concentrations.
    • Acids donate protons (H+). Bases accept protons.
    • Example: HCN (weak acid) in water: HCN + H2O ↔ H3O+ + CN-. Knowing the Ka value, you can calculate the pH of the solution.

    Acid-Base Reactions and Buffers

    • Strong acid + strong base: H+ + OH- → H2O
    • Weak acid + strong base: HA + OH- → H2O + A-
    • Weak base + strong acid: B + H+ → BH+
    • Weak acid + weak base: HA + B → A- + BH+
    • Buffers are solutions containing significant concentrations of a weak acid and its conjugate base; they stabilize pH and react with added strong acids or bases to minimize pH change.

    Acid-Base Titrations

    • Titration involves gradually adding a solution of known concentration to a solution of unknown concentration.
    • Equivalence point: The point where moles of acid and base are equal.
    • Strong acid-strong base titration: Equivalence point at pH = 7
    • Weak acid-strong base titration: Equivalence point at pH > 7
    • Weak base-strong acid titration: Equivalence point at pH < 7
    • Halfway to the equivalence point, pH = pKa.

    Molecular Structure and Acid/Base Strength

    • Stronger acids have higher Ka values.
    • Electronegativity impacts acid strength: More electronegative elements stabilize the conjugate base, making the acid stronger.
    • Stronger acids form weaker conjugate bases.
    • Stronger bases form weaker conjugate acids.

    pH and pKa

    • pH > pKa: more conjugate base than weak acid
    • pH < pKa: more weak acid than conjugate base
    • Buffer solution: contains a weak acid and its conjugate base.
      • pH is higher than pKa: more conjugate base
      • pH is lower than pKa: more weak acid

    Properties of Buffers

    • Buffering capacity:
      • Ability to resist pH changes.
      • Higher buffering capacity with greater concentrations of weak acid and conjugate base.
      • Highest buffering capacity when concentrations of weak acid and conjugate base are approximately equal.
    • Buffers have higher buffering capacity against acids if the buffer has more conjugate base, and vice versa.

    Henderson-Hasselbalch Equation

    • pH = pKa + log([A-]/[HA])
    • Calculates pH of a buffer solution.
    • In a perfect buffer ([A-] = [HA]), pH = pKa.

    Buffering Capacity

    • Buffering capacity can be affected by changes in concentration of the weak acid or conjugate base.
    • Impurities in buffer components can alter pH.
    • Buffering capacity against acids is greater with more conjugate base.
    • Buffering capacity against bases is greater with more weak acid.

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    Test your understanding of the fundamental concepts of acids and bases. This quiz covers pH calculations, the differences between strong and weak acids/bases, and how temperature affects pH. Perfect for chemistry students looking to solidify their knowledge!

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