Molarity Formula
The molarity formula M = moles/volume calculates the concentration of a solution.
Essential for chemistry lab work and solution preparation.
The Formula
M = n / V
Molarity measures how concentrated a solution is. It tells you how many moles of solute are dissolved in each liter of solution.
Variables
| Symbol | Meaning |
|---|---|
| M | Molarity (measured in moles per liter, mol/L or M) |
| n | Number of moles of solute (mol) |
| V | Volume of solution (measured in liters, L) |
Example 1
You dissolve 0.5 moles of NaCl in 2 liters of water. What is the molarity?
Identify the values: n = 0.5 mol, V = 2 L
Apply the formula: M = n / V = 0.5 / 2
M = 0.25 mol/L (or 0.25 M)
Example 2
You need 500 mL of a 0.1 M HCl solution. How many moles of HCl do you need?
Convert volume: V = 500 mL = 0.5 L
Rearrange: n = M × V = 0.1 × 0.5
n = 0.05 mol
When to Use It
Use the molarity formula when working with solutions in chemistry.
- Preparing solutions of a specific concentration
- Stoichiometry calculations involving solutions
- Titration calculations
- Determining how much solute to add to achieve a target concentration