Calculate the mass fraction of sodium hydroxide in the solution obtained by mixing 200 g

Calculate the mass fraction of sodium hydroxide in the solution obtained by mixing 200 g of a 5% solution and 300 g of a 20% solution of this substance.

The mass fraction of sodium hydroxide is determined by the formula:

w = m (NaOH) / m (solution) * 100%.

From the known data, we first find how much g of salt is in the first and second solutions.

1.5% = x / 200 * 100%.

Hence, x = 10 g NaOH.

2.20% = y / 300 * 100%.

Hence y = 60 g NaOH.

When mixing solutions, the mass of sodium hydroxide is made up of its masses in both solutions:

m = 10 + 60 = 70 g.

Then the mass fraction of NaOH in the new solution:

w = 70 / (200 + 300) * 100% = 14%.