# Molar Concentration Formula

MolarÂ concentrationÂ isÂ theÂ mostÂ effectiveÂ wayÂ ofÂ describingÂ aÂ soluteÂ concentrationÂ inÂ aÂ solution. Molarity is described as the total number of moles of solute dissolved in per liter of solution,i.e., M = mol/L.Â  All moles measurements are applied to determine the volume of moles in the solution that is the molar concentration.

## Formula of Molar Concentration

The molar concentration formula is given by,

Molar Concentration = Amount in Moles / Volume of Solution

### Solved Examples

Example 1

Determine the molar concentration of NaOH for the reaction between HCl and NaOH.

Solution:

The balanced chemical equation can be framed as,

HCl + NaOH â†’ NaCl + H2O

For an acid

n(HCl) = (35.0 / 1000Â dm3) Ã— 0.250 mol dm-3

Â Â Â Â Â Â Â Â Â Â = 8.75 Ã—Ã— 10-3mol

The mole ratio NaOH : HCl = 1:1.

The amount of NaOH present in moles is 8.75 Ã— 10-3mol.

Now we have the equation,

Molar Concentration = Amount in Moles / Volume of Solution

First convert the volume of aqueous NaOH into dm-3

25 cm3 = 25 / 1000 dm3

Â Â Â Â Â Â Â Â Â Â Â Â = 25 Ã— 10-3dm3

Therefore, the molar concentration of NaOH

Â Â Â Â Â Â Â Â Â Â Â = 8.75Ã—10âˆ’3 / 25.0Ã—10-3

Molar concentration of NaOH = 0.350 mol dm-3

Example 2

The concentration of Ca(HCO3)2 is 0.85 gmol/L. Convert this concentration into geq/L.

Solution:

Given :

[C] = 0.85 gmol/ L

[C]eq = [C][MM] / eq.mass

MM = 40.1(2) + 2{1+12+3(16)}

Â Â  = 202.2

Number of reference species = 2

Therefore, eq.mass = Ca(HCO3)2 / 2

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Â = 202.2 / 2

[C]eq = 0.85[202.2] / 202.2/2

= 1.7 geq/L