Potassium chromate is used as an indicator in titrations for the determination of chloride ion. At the end-point of a titration of an aqueous solution of a metal chloride salt (e.g. NaCl) against silver nitrate solution in the presence of potassium chromate, red Ag₂CrO₄ precipitates. Give equations for the pertinent reactions occurring during the titration, and, using relevant data from Table 7.5, explain how the indicator works.

Table 7.5

Transcribed Image Text:

Compound Barium sulfate Calcium carbonate Calcium hydroxide Calcium phosphate Iron(II) hydroxide Iron (II) sulfide Iron(III) hydroxide Lead(II) iodide Lead(II) sulfide Magnesium carbonate Magnesium hydroxide Silver(1) chloride Silver(1) bromide Silver(1) iodide Silver(1) chromate Silver(1) sulfate Formula BaSO4 CaCO3 Ca(OH)2 Ca3(PO4)2 Fe(OH)2 FeS Fe(OH)3 Pbl₂ PbS MgCO3 Mg(OH)2 AgCl AgBr Agl Ag2 CrO4 Ag₂SO4 K(298 K) 1.07 x 10-10 4.96 × 10-⁹ 4.68 x 10-6 2.07 x 10-33 4.87 x 10-¹7 6.00 × 10-19 2.64 x 10-3⁹ 8.49 × 10-⁹ 3.00 x 10-28 6.82 x 10-6 5.61 x 10-12 1.77 x 10-10 5.35 x 10-13 8.51 x 10-17 1.12 x 10-¹2 1.20 x 10-5