Molar Concentration Formula

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 → NaCl + H₂O

For an acid

n(HCl) = (35.0 / 1000 dm³) × 0.250 mol dm^-3

          = 8.75 ×× 10^-3mol

The mole ratio NaOH : HCl = 1:1.

The amount of NaOH present in moles is 8.75 × 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

            = 25 × 10^-3dm³

Therefore, the molar concentration of NaOH

           = 8.75×10⁻³ / 25.0×10^-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)}

   = 202.2

Number of reference species = 2

Therefore, eq.mass = Ca(HCO₃)₂ / 2

                  = 202.2 / 2

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

= 1.7 geq/L