146. Solving a chemistry problem

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• (2) A sample of a standard aluminum alloy containing 12.50% Si, weighing 0.3000 g, was dissolved in a 500.0 ml flask. To construct the calibration curve, 5.00 were placed in volumetric flasks with a capacity of 100.0 ml; 5.20; 5.40; 5.60; 5.80; 6.00 ml of this solution, added reagents - solutions of ammonium molybdate and iron (II) sulphate and brought to the mark. Optical densities relative to the first solution were measured and obtained:

Vst, ml 5.20 5.40 5.60 5.80 6.00

Aotn 0.105 0.215 0.330 0.440 0.550

A sample of the analyzed alloy weighing 0.2500 g was dissolved in a flask with a capacity of 500.0 ml. A sample of 5.00 ml was placed in a 100.0 ml volumetric flask, reagents were added and the relative density was measured, as in the construction of the calibration curve.

Calculate the mass fraction (%) of silicon in the samples according to the following data:

• Aot.x = 0.360

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