In 270 g of water, 30 g of salt is dissolved. Determine the mass fraction of salt in the solution.

Given:
m (H2O) = 270 g
m (salt) = 30 g
To find:
W =?
Decision:
1) Let’s write formulas for solving the problem.
W = (m substance: m solution) x 100%
m solution = m solute + m solvent
2) Find the mass of the solution:
m solution = 30 g + 270 g = 300 g.
3) Find the mass fraction:
W = (30: 300) x 100% = 10%
Answer: W = 10%.