Remember: Always follow appropriate lab safety procedures when mixing and storing chemicals.  

When a substance, called a solute, is dissolved in another substance, called the solvent, a solution is formed. A solution is a uniform distribution of solute in solvent. For example, vinegar is a solution of acetic acid, the solute, in water, the solvent. The amount of solute in a solvent is important and can be expressed in several different ways. Some common units of concentration will be discussed in this manual.
  

Molarity (M) means the number of moles of solute per liter of solution. To prepare a 1 M solution, slowly add 1 g formula weight of compound to 500-mL distilled or deionized water in a 1000-mL volumetric flask half filled with distilled or deionized water. Allow the compound to dissolve completely, swirling the flask gently if necessary. Once the solute is completely dissolved and the solution is at room temperature, dilute to the mark with water. Invert the flask several times to mix.

To make a 1 M solution of sodium hydroxide, slowly add 40 g sodium hydroxide to 500 mL distilled or deionized water in a 1000-mL volumetric flask. When all the solid is dissolved and the solution is at room temperature, dilute to the mark and invert the flask several times to mix.

To make a 1 M solution of acetic acid, dissolve 60.05 g acetic acid in 500 mL distilled or deionized water in a 1000-mL volumetric flask. Since acetic acid is a liquid, it  may also be measured by volume. Divide the mass of the acid by its density (1.049 g/mL) to determine the volume (57.24 mL). Use either 60.05 g or 57.24 mL acetic acid to make the solution. Swirl the flask gently to mix the solution. When the solution is at room temperature, dilute to the mark and invert the flask several times to mix.
  

Mass percent means the number of grams of solute per 100 g of solution. For example, 10 g sodium chloride in 90 g water is a 10% by mass solution.

Volume percent means the number of milliliters of solute per 100 mL of solution. The volume percent of a solution cannot be calculated directly from the volumes of its components because the final volume may not equal the sum of the components’ volumes. To prepare volume percent solutions, first determine the final volume and concentration of the desired solution and then determine the amount of solute. Dilute the solute in sufficient solvent to produce the final volume of  desired solution. For example, to prepare 100 mL of a 10% by volume solution of acetic acid, dilute 10 mL acetic acid with distilled or deionized water to make 100 mL of solution.

Note: Solutions of concentrated reagents, such as 37% hydrochloric acid and 85% phosphoric acid, are percent solutions by mass. In general, percent solutions are by mass.
  

When preparing a dilution, decide the volume and molar concentration of the resulting solution that you require. Use the following equation to determine how much of the concentrated reagent is needed to prepare the diluted solution, 

M _reagent x V _reagent = M _dilution x V _dilution 

where M is molarity and V is volume. 

Slowly add the calculated volume of concentrated reagent to a proper-sized volumetric flask half filled with distilled or deionized water and swirl the flask to mix. Once the solution is at room temperature, dilute to the mark with water and invert the flask several times to mix.

For example, what volume of 10 M acetic acid is required to prepare 1.0 L of 0.50 M acetic acid?

10 M x V _reagent = 0.50 M x 1.0 L
 
V _reagent = 0.050 L = 50 mL

A volume of 50 mL of 10 M acetic acid is required to prepare 1.0 L of 0.50 M acetic acid.