Acids, Bases, and pH Quiz

Grade 10 · Science · Quiz

Test your understanding of acid-base theories, the pH scale, and neutralization reactions.

Questions

  1. According to the Arrhenius theory, which of the following is classified as a base?

    1. HBr
    2. H₂SO₄
    3. KOH
    4. HNO₃
    Show answer

    Answer: KOH

    KOH is a base because it dissociates to produce OH⁻ ions in water according to Arrhenius theory

  2. What is the pH of a solution with [OH⁻] = 1 × 10⁻² mol/L at 25°C?

    1. 2
    2. 4
    3. 10
    4. 12
    Show answer

    Answer: 12

    pOH = -log(10⁻²) = 2. pH = 14 - pOH = 14 - 2 = 12

  3. In the reaction NH₃ + H₂O ⇌ NH₄⁺ + OH⁻, water is acting as:

    1. A Brønsted-Lowry acid
    2. A Brønsted-Lowry base
    3. An Arrhenius base
    4. A neutral solvent only
    Show answer

    Answer: A Brønsted-Lowry acid

    Water donates H⁺ to NH₃ (which accepts it), making water the Brønsted-Lowry acid and NH₃ the base

  4. What volume of 2.0 M NaOH is needed to neutralize 50 mL of 1.0 M HCl?

    1. 100 mL
    2. 50 mL
    3. 25 mL
    4. 10 mL
    Show answer

    Answer: 25 mL

    Moles HCl = 0.050 L × 1.0 mol/L = 0.05 mol. Volume NaOH = 0.05 mol ÷ 2.0 mol/L = 0.025 L = 25 mL

  5. Which indicator would be most appropriate to detect the endpoint of a strong acid-strong base titration?

    1. Litmus (changes at pH 7)
    2. Phenolphthalein (changes pH 8.2-10)
    3. Methyl orange (changes pH 3.1-4.4)
    4. Both phenolphthalein and litmus work equally well
    Show answer

    Answer: Both phenolphthalein and litmus work equally well

    For a strong acid-strong base titration, the equivalence point is at pH 7. Both litmus (changes ~7) and phenolphthalein work adequately; phenolphthalein is more commonly used in practice

  6. A weak acid has a Ka of 1.8 × 10⁻⁵. Compared to a strong acid, a weak acid of the same concentration will:

    1. Have a lower pH (more acidic)
    2. Have a higher pH (less acidic)
    3. Have the same pH
    4. Not affect pH at all
    Show answer

    Answer: Have a higher pH (less acidic)

    Weak acids only partially dissociate, producing fewer H⁺ ions than a strong acid at the same concentration, resulting in a higher (less acidic) pH

  7. A buffer solution is most effective when the pH is close to the pKa of the weak acid component.

    Show answer

    Answer: True

    Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA]). When pH ≈ pKa, concentrations of acid and base are equal and the buffer capacity is maximum

  8. The conjugate base of H₂CO₃ (carbonic acid) is ________.

    Show answer

    Answer: hco₃⁻

    H₂CO₃ donates one H⁺ to become HCO₃⁻ (bicarbonate), which is its conjugate base

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