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pH and pOH quiz #4

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Terms in this set (40)

  • Why does pure water have a neutral pH?
    Because [H+] = [OH–] due to autoionization.
  • The value of Kw at 40°C is 3.0 x 10^-14. What is the pH of pure water at 40°C?
    pH = -log(√Kw) = -log(√3.0 x 10^-14) ≈ 6.77
  • What is the hydroxide ion concentration in a solution of pOH 8.14?
    [OH–] = 10^-8.14 ≈ 7.24 x 10^-9 M
  • What will be the pH of a solution with a hydroxide concentration of 4.3 x 10^-2 M?
    pOH = -log(4.3 x 10^-2) ≈ 1.37; pH = 14 - 1.37 = 12.63
  • What is the pH of a 1.6 M solution of HClO4?
    pH = -log(1.6) ≈ -0.20
  • What is the pH of a substance that has a hydrogen ion concentration of 1.2 x 10^-2 M?
    pH = -log(1.2 x 10^-2) ≈ 1.92
  • Which solution has the highest pH among 0.1 M NaOH, 0.1 M HCl, 0.1 M CH3COOH, and 0.1 M NH4Cl?
    0.1 M NaOH.
  • What is the pH of a 1.8 M solution of HClO4?
    pH = -log(1.8) ≈ -0.26
  • What is the pH of a solution with a hydrogen (H+) ion concentration of 10^-4 M?
    pH = 4
  • What is the pH of a 0.6 M HNO3 solution?
    pH = -log(0.6) ≈ 0.22
  • What is the relationship between the pH scale and concentration?
    pH is the negative logarithm of the H+ concentration.
  • Which pH value corresponds to the highest concentration of hydronium?
    Lowest pH value.
  • What is the concentration of hydroxide ions in a solution with a pH of 11.8?
    pOH = 14 - 11.8 = 2.2; [OH–] = 10^-2.2 ≈ 6.3 x 10^-3 M
  • Which property of a substance can be determined using a pH indicator?
    Acidity or basicity (pH).
  • At what times should a pH electrode be submerged in a solution?
    During pH measurement.
  • Which of these correctly defines the pH of a solution?
    pH is the negative logarithm of the hydrogen ion concentration.
  • What is the pH of a solution with [H+] = 1.25 x 10^-10 M? Use: -10.1, -9.90, 7.90, 9.90
    pH = -log(1.25 x 10^-10) ≈ 9.90
  • Why is the pH of pure water at 37°C approximately 6.8?
    Kw increases with temperature, lowering the neutral pH.
  • A solution of ammonia has a pH of 11.8. What is the concentration of OH– ions in the solution?
    pOH = 14 - 11.8 = 2.2; [OH–] = 10^-2.2 ≈ 6.3 x 10^-3 M
  • What is the ratio of H+ ions to OH– ions at a pH = 8?
    [H+] / [OH–] = 10^-8 / 10^-6 = 0.01
  • Which solution has a pH of 7.00: pure water, 0.1 M HCl, 0.1 M NaOH, or 0.1 M CH3COOH?
    Pure water.
  • What is [H+] in a 0.270 M solution of acrylic acid?
    Calculate using Ka and ICE table for weak acid.
  • The pH of a basic solution is 8.11. What is [H+]?
    [H+] = 10^-8.11 ≈ 7.76 x 10^-9 M
  • If the pH at the half-titration point of a monoprotic weak acid is 4.2, what is the pKa?
    pKa = 4.2
  • The pH of an acidic solution is 2.11. What is [H+]?
    [H+] = 10^-2.11 ≈ 7.76 x 10^-3 M
  • What is the pH of a neutral solution at a temperature where Kw = 2.3 x 10^-14?
    pH = -log(√2.3 x 10^-14) ≈ 6.84
  • A solution has a [H3O+] = 3.2 x 10^-3 M at 25°C. What is the [OH–] of the solution?
    [OH–] = Kw / [H3O+] = 1 x 10^-14 / 3.2 x 10^-3 ≈ 3.13 x 10^-12 M
  • The pOH of an acidic solution is 11.63. What is [OH–]?
    [OH–] = 10^-11.63 ≈ 2.34 x 10^-12 M
  • What is the pH of a 0.750 M solution of NaCN (Ka of HCN is 4.9 x 10^-10)?
    Calculate using hydrolysis of CN–; solution is basic.
  • What is the pH of a 0.0820 M solution of methylamine (CH3NH2)?
    Calculate using Kb and ICE table for weak base.
  • The pOH of an acidic solution is 10.29. What is [H+]?
    pH = 14 - 10.29 = 3.71; [H+] = 10^-3.71 ≈ 1.95 x 10^-4 M
  • What is the pOH of a 100 mL solution of 0.7 M HL?
    pOH = 14 - pH; calculate pH from [H+], then pOH.
  • What is the [H3O+] for a solution at 25°C that has pOH = 5.640?
    pH = 14 - 5.640 = 8.36; [H3O+] = 10^-8.36 ≈ 4.37 x 10^-9 M
  • The pH of a basic solution is 10.15. What is pOH?
    pOH = 14 - 10.15 = 3.85
  • An acid has a Ka of 1.34 x 10^-6. What is the pH of a 0.509 M solution?
    Use ICE table and Ka to solve for [H+], then pH = -log[H+].
  • What is the pH of a 0.200 M CH3NH3Br solution? Kb of CH3NH2 = 4.4 x 10^-4?
    Calculate using Ka for CH3NH3+ and ICE table.
  • Determine the pH of 0.036 M formic acid (HCO2H).
    Use Ka and ICE table to solve for [H+], then pH = -log[H+].
  • The pH of an acidic solution is 4.15. What is pOH?
    pOH = 14 - 4.15 = 9.85
  • Which solution will have the highest pH? The Ka of HClO is 3.8 x 10^-8.
    The solution with the lowest acid concentration or highest base concentration.
  • What is the pH of a 0.0080 M solution of potassium hydroxide (KOH)?
    pOH = -log(0.0080) ≈ 2.10; pH = 14 - 2.10 = 11.90