1. Understand Mass Percent

Mass percent is a way to express the concentration of a solution. It tells you the mass of solute (the substance being dissolved) per 100 grams of solution.

2. Formula

Mass percent = (Mass of solute / Mass of solution) x 100%

3. Apply to Your Problem

* Mass of solute (calcium chloride): 30 g

* Mass of solvent (water): 250 g

* Mass of solution: 30 g + 250 g = 280 g

4. Calculate

Mass percent = (30 g / 280 g) x 100% = 10.71%

Answer: The solution contains 10.71% calcium chloride by mass.