157. A sample of steel weighing m (g) was dissolved in a flask with a capacity of 50.0 ml. Two 20.0 ml samples were placed in 50.0 ml flasks. A solution containing 0.003000 g of vanadium was added to one flask. Hydrogen peroxide was added to both flasks and brought to the mark. Calculate the mass fraction (%) of vanadium in steel if the following optical densities Ax and Ax+st were obtained during photometry of solutions:
Option 157
m, g 0.6572
Ah 0.230
Ah+st 0.510

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