# Molarity

*A chemistry teacher who teaches General Chemistry at the K-12 level..*

## Molarity

Molarity, an expression of concentration is expressed as a ratio of moles of solute to volume of solution in Litres or dm^3.

## Molarity Calculations

Molarity calculations are important in all stages of learning -from High School Chemistry to Graduate research.

Molarity is one of the popular ways in which concentration of a solute is expressed.

Every binary solution has two components- solute and solvent. When the solute is expressed as the number of moles and the solution used is expressed in units of Litres or dm^3 then it is termed as molarity.

This introductory article gives you the basic calculations you will encounter in preparing molar solutions or solving numericals based on molarity.

We use M or mol/L as unit for molarity.

1 Liter = 1000 mL.

The General format for solving any numerical problem must include

- The information given to you in the problem along with the appropriate units
- You must then write the formula that you will use to solve the numerical
- At times you will have to modify the formula suited to the needs of the problem
- Then, substitute the given values in your formula
- Finally, calculate and give the final answer with appropriate units

__Types of problems to calculate molarity__

1. **Type 1**

*Problems where you are directly asked to calculate the molarity*

**What is the molarity of a 0.30 liter solution containing 0.50 moles of NaCl?**

Given:

Moles of NaCl= 0.5 mol

Volume of solution= 0.3L

Formula: M=n/V

Substitution: M= 0.5mol/0.3L

Final answer= 1.67 M

2. **Type 2**

*Problems that use V= n/M*

**Calculate the volume of a 3.50 molar solution of H2SO4 made from 3mol of H2SO4.**

Problems that use n=VXM

How many moles of NaOH are in 55.0 liters of a 3.00 M solution?

Given:

Volume of solution =55 L

Molarity = mol/L= 3.00 M

Moles =?

Formula n= VM

Substitute

Number of moles n= = 3.00 mol /L X 55 L= 165 mol

## Calculate -

moles | Volume | Molarity |
---|---|---|

0.5 | ? | 0.01M |

? | 3L | 0.25 M |

0.1 | 5L | ? |