Molarity (M)

Definition

Molarity (M) is a measure of the concentration of a solute in a solution, expressed as moles of solute per liter of solution. It is commonly used to quantify the concentration of chemical solutions in laboratory settings.

5 Must Know Facts For Your Next Test

1. Molarity (M) can be calculated using the formula $M = \frac{n}{V}$, where $n$ is the number of moles of solute and $V$ is the volume of the solution in liters.
2. A 1 M solution contains one mole of solute per liter of solution.
3. Molarity is temperature-dependent because it involves volume, which can expand or contract with temperature changes.
4. To prepare a specific molarity, you need to dissolve the appropriate amount of solute in enough solvent to reach the desired final volume.
5. Dilution calculations involving molarity often use the equation $M_1V_1 = M_2V_2$, where $M_1$ and $M_2$ are initial and final molarities, respectively, and $V_1$ and $V_2$ are initial and final volumes.

Review Questions

• What is the formula for calculating molarity?
• How would you prepare 500 mL of a 2 M NaCl solution?
• Why does molarity change with temperature?

Related terms

Solute: The substance that is dissolved in a solvent to form a solution.

Solvent: The substance that dissolves the solute to form a solution; typically present in greater amount.

Molality (m): A measure of concentration defined as moles of solute per kilogram of solvent.