119. Задачка по химии №011 986

115. Give a conclusion on the quality of the substance of calcium chloride in terms of quantitative content, if, according to the method of complexometric determination, 18.3 ml of a 0.05 M solution of Trilon B (K = 1.0000) was used for titration of a sample of the substance 0.7989 g, and for the control experiment – 0.15 ml of the same titrant.

Method: about 0.8 g of the substance (accurately weighed), weighed in a resealable weighing bottle, dissolved in water and transferred to a 100 ml volumetric flask, made up to the mark with water and mixed thoroughly. To 25 ml of the solution, add 5 ml of an ammonia buffer solution, 0.1 g of an acid chromium dark blue indicator mixture and titrate with a 0.05 M solution of Trilon B until a blue-violet color is obtained. The content of calcium chloride hexahydrate in the substance must be at least 98.0%. M.m of calcium chloride hexahydrate 219.05.

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