Calculate the mass fraction of the solution obtained by dissolving 10 g of salt in 30 g of water.

Given:
m (salt) = 10 g
m (water) = 30 g

Find:
ω (salt) -?

1) Calculate the mass of the resulting salt solution:
m solution (salt) = m (salt) + m (water) = 10 + 30 = 40 g;
2) Calculate the mass fraction of salt in the resulting solution:
ω (salt) = m (salt) * 100% / m solution (salt) = 10 * 100% / 40 = 25%.

Answer: The mass fraction of salt in the resulting solution is 25%.