Molarity provides connection between moles of a solute and the volume of its solution. The definition provided serves as a tool for calculating molarity from the values of moles of solute and volume of solution. The molarity of a solution is calculated by taking the moles of solute and dividing by the liters of solution.

Molarity = $\frac{Moles\ of\ solute}{Liters\ of\ solution}$

Molarity is the tool we use to write an equivalence between moles of solute and volume of solution, from which appropriate conversion factors can be formed.

## Molarity Formula Problems

Some of the solved problems based on Molarity formula is gien below:

Question 1: There are 150g of salt in 500mL of a saline soluion. What is the molarity of this solution?
Solution:
As before, NaCl has a gram molecular weight of 58.44g/mol. We are using 150g of NaCl, and the volume we want is 0.5L. Now plug these values into the molarity formula.

M = $\frac{\frac{g}{L}}{gmw}$ = $\frac{g}{L} \times \frac{1\ mol}{gmw}$

M = $\frac{\frac{150\ g}{0.5L}}{58.44g\ mol^{-1}}$

M = $\frac{151g}{0.5L} \times \frac{1\ mol}{58.44g}$

M = 5.13347 mol/L

Thus, the concentration of this solution is approximately 5.13 mol/L = 5.13M.

Question 2: Calculate the molarity of NaOH in the solution which is prepared by dissolving 4g in enough water to form 250mL of the solution.
Solution:
Molar mass of NaOH = 40g

4.00g of NaOH = $\frac{4}{40}$

= 0.01 mole of NaOH

Molarity = $\frac{Moles\ of\ solute}{Given\ volume (L)}$ $\times$ 1(L)

Molarity = $\frac{0.1}{0.25}$ $\times$ 1 = 0.4 mol L-1

Molarity = 0.04M

Therefore, the molarity of NaOH is 0.04 M.