WHAT IS MOLARITY??

Molarity is the concentration of a solution expressed as the number of moles ofsolute per litre of solution:

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

Molarity=moles of solutelitres 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:

1. Calculate the number of moles of solute present.
2. Calculate the number of litres of solution present.
3. 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

Moles of NaOH=15.0g NaOH×1 mol NaOH40.00g NaOH=0.375 mol NaOH

Litres of solution=225mL soln×1 L soln1000mL soln=0.225 L soln

Molarity=moles of solutelitres of solution=0.375 mol0.225 L=1.67 mol/L

Some students prefer to use a "molarity triangle".

labscience10ablock.wikispac

ANY PROBLEMS??

It summarizes the molarity formulas as

Moles=molarity × litres

Molarity=moleslitres

Litres=molesmolarity