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Solution concentrations and titration calculationsEdexcel A-Level Chemistry: Flashcards

What these 13 flashcards ask

  • What is the formula linking concentration, amount and volume?
  • How do you convert a concentration in mol dm⁻³ to g dm⁻³?
  • How do you convert 25.0 cm³ to dm³?
  • What are concordant titres?
  • Which result is never used in the mean titre?
  • What colour change does phenolphthalein show?
  • What colours does methyl orange show?
  • Why is the pipette rinsed with the solution it will deliver?
  • Why is a solid acid used for a standard solution?
  • How do you weigh a solid by difference?
  • In what ratio do H₂C₂O₄ and NaOH react?
  • What must be done at the volumetric flask's mark?
  • Why are rinsings of the beaker and funnel added to the volumetric flask?

Exam questions on Solution concentrations and titration calculations

  1. A school technician prepares sodium hydroxide and hydrochloric acid solutions of known concentration for a titration practical. Use relative atomic masses H = 1.0, O = 16.0, Na = 23.0 and Cl = 35.5.
    Calculate the mass of sodium hydroxide needed to make 500 cm³ of a solution of concentration 0.150 mol dm⁻³.2 marks
  2. A student titrates 25.0 cm³ portions of sodium hydroxide solution of unknown concentration with 0.100 mol dm⁻³ hydrochloric acid from a burette, repeating the titration until concordant results (within 0.10 cm³ of each other) are obtained. The equation is NaOH + HCl → NaCl + H₂O.
    The mean titre is 21.60 cm³. Calculate the concentration of the sodium hydroxide solution in mol dm⁻³.2 marks
  3. A student prepares a standard solution of ethanedioic acid by dissolving 1.575 g of ethanedioic acid dihydrate, H₂C₂O₄·2H₂O (M = 126.0 g mol⁻¹), in water and making the solution up to 250.0 cm³ in a volumetric flask. The student then titrates 25.0 cm³ portions of this solution against sodium hydroxide solution of unknown concentration, using phenolphthalein, and obtains a mean titre of 22.40 cm³. The equation is H₂C₂O₄ + 2NaOH → Na₂C₂O₄ + 2H₂O.
    Calculate the concentration of the standard solution of ethanedioic acid in (i) mol dm⁻³ and (ii) g dm⁻³ of the dihydrate.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).