To 30 grams of a 15% alkali solution, 60 grams of a 20% solution were added to find the omega of the resulting solution.

Progress:
1) Calculation of the mass of the solute of the 1st solution.
2) Calculation of the mass of the solute of the 2nd solution.
3) Calculation of the mass of the solute in the resulting solution.
4) Calculation of the total mass of the solution after adding the 2nd alkali solution.
5) Calculation of the mass fraction of the substance in the resulting solution.
Formulas:
To find the mass fraction of a substance in a solution:
W = (m.w – wa / m.r – pa) * 100%.
To find the mass of the solute:
m.w – wa = (W * m.r – pa) / 100%.
1.15 * 30/100 = 4.5g.
2.20 * 60/100 = 12g.
3.12 + 4.5 = 16.5g.
4.30 + 60 = 90g.
5.16.5 / 90 * 100 = 18.3%. – answer.