You need to make an aqueous solution of 0.202 M calcium bromide for an experiment in lab, using a 125 mL volumetric flask. How much solid calcium bromide should you add?

You need to make an aqueous solution of 0.202 M which equal to 0.202 mol/liter. If you only have 125ml solute, then the amount of calcium bromide needed would be:

concentration = mass / volume

0.202 mol / 1000ml = mass / 125ml

weight = (0.202 mol / 1000ml) * 125ml = 0.02525 mol

If you need to convert the mass into g it would be: 0.02525 mol * 200g/mol = 5.05 grams