5 grams of salt was added to 450 grams of a 4% solution. Find the mass fraction of salt in the resulting solution.

Given:
m1 solution (salt) = 450 g
ω1 (salt) = 4%
m2 (salt) = 5 g

To find:
ω3 (salt) -?

1) m1 (salts) = ω1 * m1 solution / 100% = 4% * 450/100% = 18 g;
2) m3 (salt) = m1 + m2 = 18 + 5 = 23 g;
3) m3 solution (salt) = m1 solution + m2 = 450 + 5 = 455 g;
4) ω3 (salt) = m3 * 100% / m3 solution = 23 * 100% / 455 = 5%.

Answer: The mass fraction of salt is 5%.