Prepare a Solution

Here's a quick overview of how to prepare a solution when the final concentration is expressed as M or molarity.

You prepare a solution by dissolving a known mass of solute (often a solid) into a specific amount of a solvent. One of the most common ways to express the concentration of the solution is M or molarity, which is moles of solute per liter of solution.

Example:

Prepare 1 liter of 1.00 M NaCl solution.

First calculate the molar mass of NaCl which is the mass of a mole of Na plus the mass of a mole of Cl or 22.99 + 35.45 = 58.44 g/mol

1. Weigh out 58.44 g NaCl.
2. Place the NaCl in a 1 liter volumetric flask.
3. Add a small volume of distilled, deionized water to dissolve the salt.
4. Fill the flask to the 1 L line.

If a different molarity is required, then multiply that number times the molar mass of NaCl. For example, if you wanted a 0.5 M solution, you would use 0.5 x 58.44 g/mol of NaCl in 1 L of solution or 29.22 g of NaCl.