Q6(a). Sulphate as barium sulphate by the filtering-crucible method
Consider the gravimetric estimation of sulphate as barium sulphate through filtering crucible method. (i) Mention the principle of this estimation with the requisite equation along with the ignition temperature of the precipitate. (ii) Find out the Gravimetric Factor (GF) of sulphate in barium sulphate. [Given: Atomic weight of Barium = 137.33; Atomic weight of Sulphur = 32.064; Atomic weight of Oxygen = 15.999] (iii) How can the experimentally obtained results be lower or higher than the true value? Suggest some measures in this respect so as to obtain a satisfactory result.
Answer in brief
(i) Ba²⁺ + SO₄²⁻ → BaSO₄↓ from hot, dilute HCl, ignited at about 800 °C; (ii) GF = 0.4116; (iii) low from solubility, fine-particle losses, reduction; high from coprecipitated Ba salts and occluded water.
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Coversgravimetric analysisbarium sulphategravimetric factorcoprecipitationdigestion of precipitaterelative supersaturation
All parts of Question 6
- 6(a) Sulphate as barium sulphate by the filtering-crucible method15 marks
- 6(b) Equivalence-point potential: Fe²⁺ with dichromate at pH 115 marks