Use ratio and proportion to determine the amount of hydrate needed.

111.1 g/mol anhydrous

0.200 g anhydrous

---------------------- = ------------------

147.1 g/mol hydrate

x g hydrate

(147.1 g/mol hydrate) (0.200 g anhydrous)

x g hydrate = --------------------------------------

111.1 g/mol anhydrous

x g hydrate = 0.265 g

When a solution has a liquid solute in a liquid solvent, percent concentration is

expressed as volume per unit volume (v/v). When a number expressing a liquid solute

in a liquid solvent is followed by a percent symbol (%) then the concentration is a v/v

concentration.

a. **Problem Solving**. Methods developed earlier for solving weight per volume

solutions may be applied to volume per volume solutions.

b. **Example 1**. How much alcohol is required to make 100 mL of a 20.0 mL/dL

alcohol solution?

Solution. Read the problem carefully and determine the unknown quantity.

Milliters of alcohol.

Express the volume in deciliters.

1 dL

100 mL X -------- = 1.00 dL

100 mL

Multiply the volume expressed in deciliters times the percent concentration to

determine the volume of solute needed to prepare the solution.

20.0 mL

1.00 dL X -------- = 20.0 mL

dL

MD0837

2-15

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