Mixed 45 g of 38% and 320 g of 5% hydrobromic acid. Establish the mass fraction (in%) of the substance in the final solution.

1) Find the mass of HBr in the first solution:

m1 (HBr) = m (p-pa 1) * ω1 (HBr) = 45 * 0.38 = 17.1 g.

2) Find the mass of HBr in the second solution:

m2 (HBr) = m (p-pa 2) * ω2 (HBr) = 320 * 0.05 = 16 g.

3) Find the mass fraction of HBr in the final solution:

m (HBr) total = m1 (HBr) + m2 (HBr) = 17.1 + 16 = 33.1 g.

m (p-pa 3) = m (p-pa 1) + m (p-pa 2) = 45 + 320 = 365 g.

ω3 (HBr) = m (HBr) total / m (p-pa 3) = 33.1 / 365 * 100% = 9.07%

Answer: 9.07%.