Methods of Expressing the Concentration of a Solution

Methods of Expressing the Concentration of a Solution

The concentration of a solution can be expresses in a number of ways. The important methods are:

 

  1. Mass/Weight Percentage: (w/W)

It is defined as the amount of solute in grams present in 100 grams of the solution. \small Mass\ Percentage=\frac{Mass\ of\ Solute}{Mass\ of \ Solution}\times 100

Eg, 23% w/W H2SO4 means 23 gm of H2SO4 (solute) in 100 gm of solution.

 

  1. Volume Percentage (v/V)

It is defined as the volume of solute in mL present in 100 mL solution. \small Volume\ Percentage=\frac{Volume\ of\ Solute}{Volume \ of \ Solution}\times 100

Eg, 23% v/V H2SO4 means 23 ml of H2SO4 (solute) in 100 ml of solution.

 

  1. Mass Volume Percentage (W/V)

It is s defined as the mass of solute present in 100 mL of solution.  

\small \small Mass\ by\ Volume\ Percentage=\frac{Mass\ of\ Solute}{Volume \ of \ Solution}\times 100

Eg, 23% w/W H2SO4 means 23 gm of H2SO4 (solute) in 100 ml of solution.

 

  1. Mole Fraction

It is defined as the ratio of the number of moles of that component to the total number of moles of all components.

In a binary solution for 2 components, A and B.

  1. Molarity (M)

Molarity of a solution is the number of gram molecules of the solute present in one litre of the solution.

 

\small Molarity(M)=\frac{Number\ of\ moles\ of\ solute}{Volume\ of\ Solution\ in\ L}

 

Units of molarity: mol L-1

 

  1. Molality (m)

It is defined as the number of moles of solute dissolved in 1 Kg of the solvent.

 

\small Molality\ (m)=\frac{Number\ of\ moles\ of\ solute}{Mass\ of\ Solvent\ in\ kg}

 

Units of molarity: mol kg-1

 

  1. Normality (N)

It is the number of formula mass in grams present per litre of solution. In case formula mass is equal to molecular mass, formality is equal to molarity. Like molarity and normality, the formality is also dependent on temperature.

\small Formality=\frac{Weight\ of\ solute(gm)}{Formula\ weight\ of\ solute}\times \frac{1}{Volume\ of\ solutions (L)}\small F=\frac{w}{f}\times \frac{1}{V\ (L)} ...................(i)

\small F=\frac{w}{f}\times \frac{100}{V\ (mL)} ...................(ii)

Where,

  • w = weight of solute,

  • f = formula weight of solute

  • V= volume of solution

  • nf = no. of gram formula weight

\small F=n_f\times \frac{1}{V\ (L)} ...................(iii)

  1. Formality (F)

It is defined as the number of gram equivalents of the solute present in one litre of the solution.

 

\small Normality\ (N)=\frac{Number\ of\ gram\ equivalents\ of\ solute}{Volume\ of\ Solution\ in\ L}

 

  1. Parts per million

It is defined as the Number of the parts of components by Total no of parts of all components of the solution per million.

 

Post By : Divya SIngh 25 Dec, 2018 2799 views Chemistry