To 250 g of water was added 25 g of salt. Determine the mass fraction of the solute expressed as a percentage.

* The mass of the salt will be the mass of the solute.
* Find the mass of the entire solution. To do this, add the mass of water and the mass of added salt: 250 + 25 = 275g.
* We calculate the mass fraction of salt in the solution. To do this, we will use the formula: W = (mr.v – wa / mr – pa) * 100%. We substitute the available data, we get: W = (25/275) * 100 = 9%.
Answer: the mass fraction of salt in 250 g of water is 9%.