145. Solving a chemistry problem

50 (1). A portion of Na2HPO4 * 12H2O weighing 0.5046 g was dissolved in perchloric acid and diluted to 1000.0 ml. To construct the calibration graph, 10.00 20.00 25.00 30.00 35.00 ml of this solution were placed in 50.00 ml volumetric flasks, a mixture of molybdate and ammonium metavanadate was added and diluted to the mark with water. Measured optical density relative to the first solution and obtained:
U, St, ml 20.00 25.00 30.00 35.00
Aot 0.186 0.285 0.380 0.475
A portion of nitroammofoski weighing 0.3000 g was dissolved in hydrochloric acid and diluted solution to 250.0 ml. An aliquot of 20.00 ml was placed in a flask with a capacity of 50.00 ml and performed the same operations as in the construction of the calibration curve. Calculate the mass fraction of P2O5 in the NPK, if for different samples received:
Option 1
Aoth. X = 0,365