Q9(b). Ca and Mg in a mixture by EDTA
Outline the principle for the estimation of Ca²⁺ and Mg²⁺ in a mixture (solution) employing EDTA as a titrant. [Mentioning of the names of buffers, pH values, indicators, specification of colour changes, basis of the calculations are required] Draw the structures of Ca²⁺–EDTA and Mg²⁺–EDTA complexes.
Answer in brief
Two EDTA titrations: at pH 10 (NH₃–NH₄Cl, EBT, wine red → blue) for Ca + Mg; at pH 12–13 (NaOH, Mg(OH)₂ precipitated, murexide pink → violet) for Ca alone; Mg by difference.
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CoversEDTA titrationcalcium and magnesium estimationEriochrome Black Tmurexidewater hardnessmetal-EDTA complex structure
All parts of Question 9
- 9(a) Binding energy per nucleon; fusion and fission15 marks
- 9(b) Ca and Mg in a mixture by EDTA15 marks