To 400 g of a 13% solution of phosphoric acid was added 200 g of water. Calculate the mass fraction

To 400 g of a 13% solution of phosphoric acid was added 200 g of water. Calculate the mass fraction of the solute in the resulting solution.

Given:
m р1 (H3PO4) = 400 g
w1 (H3PO4) = 13% = 0.13
m (H2O) = 200 g
To find:
w2 (H3PO4)
Decision:
m p2 (H3PO4) = 400 g + 200 g = 600 g
m в1 = m в2
Let the mass fraction of the substance in the second solution be x, then
w1 * m p1 = w2 * m p2
0.13 * 400 = x * 600
52 = 600x
x = 0.0866
0.0866 * 100% = 8.66%
Answer: 8.66%