11 g of sodium hydroxide was added to 120 grams of 15% sodium hydroxide solution.

11 g of sodium hydroxide was added to 120 grams of 15% sodium hydroxide solution. Determine the mass fraction of NaOH in the resulting solution.

Find the mass of sodium hydroxide. For this we use the following formula.
W = m r.v / mr-ra × 100%.
m (NaOH) = m solution × W / 100% = 120 × 0.15 = 18 g NaOH.
We find the mass of the entire solution.
m solution = 120 + 11 = 131 g.
Next, we find the mass of the solute.
m r.w = 18 + 11 = 29 g NaOH.
Next, we find the mass fraction of sodium hydroxide in the resulting solution. We write down the solution.
W = 29g / 131g × 100% = 0.22 × 100 = 22%.
This means that the mass fraction of sodium hydroxide in the resulting solution is 22 percent.
Answer: W (NaOH) = 22%.