# What is molarity?

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#### Explanation

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Molarity is the concentration of a solution expressed as the number of moles of solute per litre of solution.

#### Explanation:

To get the molarity, you divide the moles of solute by the litres of solution.

For example, a 0.25 mol/L NaOH solution contains 0.25 mol of sodium hydroxide in every litre of solution.

To calculate the molarity of a solution, you need to know the number of moles of solute and the total volume of the solution.

To calculate molarity:

- Calculate the number of moles of solute present.
- Calculate the number of litres of solution present.
- Divide the number of moles of solute by the number of litres of solution.

**EXAMPLE**:

What is the molarity of a solution prepared by dissolving 15.0 g of NaOH in enough water to make a total of 225 mL of solution?

**Solution**:

1 mol of NaOH has a mass of 40.00 g, so

Some students prefer to use a "molarity triangle".

It summarizes the molarity formulas as

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