In case of poisoning with potassium permanganate, solutions are prepared for gastric lavage as follows

In case of poisoning with potassium permanganate, solutions are prepared for gastric lavage as follows: 1 glass (250 g) of a 3% solution of hydrogen peroxide H2O2 is added to 2 liters of water, 2 glasses of a 3% solution of acetic acid CH3COOH are added here. Determine the mass fraction of hydrogen peroxide in the resulting solution.

Let’s calculate the mass of pure hydrogen peroxide contained in the solution:
m (H2O2) = w1 (H2O2) * m (H2O2 solution) = 0.03 * 250 = 7.5 g;
m (final solution) = m (H2O) + m (H2O2 solution) + m (CH3COOH) = 2000 + 250 + 2 * 250 = 2750 g;
w2 (H2O2) = m (H2O2) / m (final solution) = 7.5 / 2750 = 0.00273 = 0.273%.
Answer: w2 (H2O2) = 0.273%.