You want to make 100 ml of a 2.5 m stock solution of calcium chloride (molecular weight 110.98 g/mol). how many grams of calcium chloride do you need to weigh out in order to make this solution? round your answer to the nearest tenth of a gram.

27.7 g

Explanation:

To solve this problem we use the definition of molarity:

From the problem we're given M = 2.5 M and volume = 0.100 L. We use the above formula and calculate the required moles of calcium chloride (CaCl₂):

Finally we use the molecular weight of calcium chloride to calculate the required mass:

Rounding to the nearest tenth of a gram the answer is 27.7 g.