Solution concentrations and titration calculationsEdexcel A-Level Chemistry: Mind map

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