A student is instructed to prepare 3.00 L of a 0.100-M solution of copper(II) sulfate. She goes...

The molar mass of copper sulfate = 159.6 g/mol

• A student is instructed to prepare 3.00 L of a 0.100-M solution of copper(II) sulfate. She goes to the stockroom and finds a 100-g bottle of anhydrous salt, which costs $14.00

The mass of copper sulfate is found as:

{eq}Molarity=\dfrac{mass}{molar \ mass \times \ volume} {/eq}

{eq}0.100\ M=\dfrac{mass}{159.6\ g/mol \times3\ L} {/eq}

Mass= 47.88 g

100 g costs $14.00, 47.88 g will cost $6.7.

• To prepare 3L of a 0.100M solution we need 300 mL out of the 500mL bottle which has a cost of $12.5. Those 300mL have a cost of 7.50$, which results in higher than the cost of the solid.

Hence, the correct answer is a 500-mL bottle of a 1-M solution will be the most economical way of making the solution.