International A LevelChemistryEdexcelExam Questions4: Rates, Equilibria and Further Organic Chemistry4.5 Acid-base Equilibria

Acid-base Equilibria (Edexcel International A Level Chemistry)

Exam Questions

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4.5 Acid-base Equilibria

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4.5 Acid-base Equilibria

1a1 mark

A graph of pH against volume of acid added for an acid-base titration is shown.

q4-paper-4-2021-june-edexcel-ial-chemistry

a)
Which acidic solution was used in the titration?

  • 0.1 mol dm–3 CH3COOH

  • 1.0 mol dm–3 CH3COOH

  • 0.1 mol dm–3 HCl

  • 1.0 mol dm–3 HCl

Choose your answer

1b1 mark
b)
Which basic solution was used in the titration?

  • NH3

  • LiOH

  • Ba(OH)2

  • NaOH

Choose your answer

1c1 mark
c)
A student suggested five indicators that might be used in this titration:

thymol blue
methyl orange
bromophenol blue
bromocresol green
phenolphthalein

How many of these indicators would be suitable? Use your Data Booklet.

  • 5

  • 4

  • 3

  • 2

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21 mark

An example of a diprotic acid is cis-butenedioic acid. Titration of this acid using sodium hydroxide solution gave the titration curve shown.

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Which indicator would be most suitable for measuring the end-point of the neutralisation of the proton in cis-butenedioic acid which has a pKa = 6.33?

Use your Data Booklet.

  • bromocresol green

  • bromothymol blue

  • litmus

  • phenolphthalein

Choose your answer

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31 mark

At 25°C, the pH of pure water is 7.00 and at 100°C, the pH of pure water is 6.14.
What can be deduced from this information?

(1)

      Enthalpy change of
dissociation of water		 Concentration of hydrogen ions
  ☐ A endothermic higher at 100°C than at 25°C
  ☐ B endothermic lower at 100°C than at 25°C
  ☐ C exothermic higher at 100°C than at 25°C
  ☐ D exothermic lower at 100°C than at 25°C

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    41 mark

    When ethanoic acid and chloroethanoic acid are mixed, an equilibrium is set up.

    CH3COOH + CH2ClCOOH ⇌ CH3COOstraight H subscript 2 superscript plus+ CH2ClCOO−

    The Brønsted-Lowry acids in this equilibrium are

    • CH3COOH and CH2ClCOOH

    • CH3COOH and CH3COObegin mathsize 16px style H subscript 2 to the power of plus sign end style

    • CH2ClCOOH and CH3COOstraight H subscript 2 superscript plus

    • CH3COOstraight H subscript 2 superscript plusand CH2ClCOO−

    Choose your answer

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    5
    Sme Calculator    1 mark

    What is the pH of 0.010 mol dm−3 aqueous calcium hydroxide, Ca(OH)2 (aq)?

    [pKw = 14]

    • 11.7

    • 12.0   

    • 12.3

    • 13.3

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    6a1 mark

    A titration was carried out by adding 0.1 mol dm−3 hydrochloric acid to
    0.1 mol dm−3 aqueous ammonia.

    HCl (aq) + NH3 (aq) rightwards arrow NH4Cl (aq)

    The titration curve is shown.

    q10-paper-4-jan-2021-edexcel-ial-chemistry

    a)
    Which region of the graph represents the most effective buffer solution?

    • region T

    • region U

    • region V

    • region W

    Choose your answer

    6b1 mark
    b)
    Which of these is the best indicator to use in this titration?

    [Refer to the Data Booklet]

    • methyl red

    • phenol red

    • phenolphthalein

    • thymol blue

    Choose your answer

    6c1 mark
    c)
    What is the approximate pH of an ammonium chloride solution?

    • 2.0

    • 5.8

    • 9.7

    • 11.3

    Choose your answer

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