Final answer:
The concentration of a solution with 30 grams of salt in a 250 grams of solution is calculated as 12 percent by mass.
Step-by-step explanation:
To calculate the concentration of a solution, we need to know the mass of the solute and the mass of the solution itself. In this case, the student has provided that there are 30 grams of salt (solute) in a 250 grams of solution. The concentration of the solution in mass/mass percent can be found using the formula:
Concentration (%) = (Mass of solute / Mass of solution) x 100%
Substituting the given values:
Concentration (%) = (30 g / 250 g) x 100% = 12%
Therefore, the concentration of the salt in the solution is 12 percent by mass.