Molarity (M) is a unit used to measure the concentration of a solution. It tells us how many moles of solute are dissolved in one liter of solution. In simple words, molarity shows how strong or weak a solution is.
For example, if the molarity of a solution is 1 M, it means there is 1 mole of solute present in 1 liter of solution.

Example:
If 58.5 g of NaCl (molar mass = 58.5 g/mol) is dissolved in 1 liter of water, then the molarity of that solution is 1 M.

Molarity Formula.

$$
M = \frac{n}{V}
$$

where:

• M = Molarity (mol/L)
• n = Moles of solute
• V = Volume of solution (in liters)

What does molarity mean?

When we say that a solution has a molarity of 1 M, it means that 1 mole of solute is dissolved in 1 liter of solution.
Example: If 58.5 g of NaCl (which has a molar mass of 58.5 g/mol) is dissolved in 1 liter of water, the molarity of that solution is 1 M.

How to Calculate Molarity (Steps)

1. Write down the mass of the solute (in grams).
2. Find its molar mass (g/mol) from the periodic table.
3. Calculate the number of moles using the formula:

$$
n = \frac{\text{mass}}{\text{molar mass}}
$$

4. Now, note the volume of the solution (in liters).
5. Apply the molarity formula:

$$
M = \frac{n}{V}
$$

That’s it! You will get the molarity in mol/L.

Example

If you have 0.5 mole of NaOH and the volume of the solution is 0.25 L, then:

$$
M = \frac{0.5}{0.25} = 2.0\,M
$$

So, the molarity of the solution is 2 M.

Useful Tips

• Always remember to convert the volume into liters (mL → L).
• If the temperature changes, the volume of the solution may also change, which can slightly affect the molarity.
• Molarity is mostly used for aqueous (water-based) solutions.

Frequently Asked Questions (FAQ) on Molarity

1. What is molarity in simple words?

Molarity tells us how many moles of solute are dissolved in one liter of solution. It shows how concentrated a solution is.

2. What is the formula for molarity?

$$ M = \frac{n}{V} $$

where M = molarity (mol/L), n = moles of solute, and V = volume of solution in liters.

3. What is the unit of molarity?

The unit of molarity is mol/L or simply M (read as “molar”).

4. How do you calculate moles from molarity?

$$ n = M \times V $$

where n = moles, M = molarity, and V = volume in liters.

5. What is the difference between molarity and molality?

Molarity (M): Moles of solute per liter of solution.
Molality (m): Moles of solute per kilogram of solvent.
Molarity depends on volume, while molality depends on mass.

6. Can molarity change with temperature?

Yes. Molarity depends on the volume of the solution, which can change with temperature.

7. What is a 1 M solution?

A 1 M (one molar) solution contains 1 mole of solute in 1 liter of solution.
Example: 58.5 g of NaCl dissolved in 1 L of water forms a 1 M NaCl solution.

8. Why is molarity important in chemistry?

Molarity helps chemists prepare solutions accurately and perform reactions, titrations, and lab experiments with correct concentrations.