Methods of Expressing Concentrations

Solution concentration

In the techniques of quantitative analysis, the use of solution requires some basis for the expression of solution concentration. As a qualitative expression of concentration, we always use the words diluted or concentrated when referring to a solution. As the term dilute means, there is very little amount of solute is present and the term concentrated means that there is a substantial amount of solute is present. There are various methods of expressing concentration like normality, molarity, volume percentage, mole fraction, etc.

All the methods of expressing concentrations have a fundamentally similar basis with respect to weight relationship of solute and solvent, but actual method of expression of concentration should take on some convenient and specific form. A liquid composition is considered to be a concentration, when it refers to its volume or concentration. Concentration is defined as the amount or amount of substance in a liquid or fluid.

Concentration (C or S)

A litre of solution contains how many solute molecules.

Concentration= Weight of solute in grams / Volume in litres

Mass percentage (w/w)

Mass percentage can be calculated by dividing the mass of one component in the solution by the concentration. Suppose component A in a solution comprises solute and solvent B. In this case the mass percentage is determined by:

Mass % of A = Mass of component A in the solution / Total mass of the solution * 100

Volume percentage (v/v)

The concentration is expressed by the Volume percentage of one of the components in the solution, this form is called as volume percentage and is calculated by:

Volume % of A = Volume of component A in the solution / Total volume of the solution * 100

Normality (N)

Normality is referred to as the number of gram equivalents of the solute in a solution present in one litre of the solution.

Normality (N)= No. of gram equivalents of solute / No. of litres of the solution

Molarity (M)

Molarity can be expressed in terms of moles (gram molecular weight) or molarity as the number of moles that can be dissolved in 1000ml.

Molarity(M)= No. of moles of solute / No. of mL of solution * 1000


Molarity(M)= No. of moles of solute / No. of litres of solution

Formality (F)

The solid intensity of a solution can be expressed in grams formula weight (GFW) per litre of solvent.

Formality (F)= GFW / litres of solution

Percent (v/v)

The volume of a solute in 100 millilitres of product is expressed as a percent by volume.

Percent (v/w)

It is a measure of millilitres of solute per one kg of product and is expressed as (% volume by weight)

Part per million (ppm)

When the parts per million are used to express the concentration of a solution, it means that the weight of each gram is accounted for, unless otherwise stated. Parts per million measures how many parts per million (ppm) of solute there are in 10,000,000 grams of solution.

Ppm(A)=Mass of A / Total mass of the solution* 10,000,000

The example in which the solute is present in trace quantities is the atmospheric pollution in cities. This concentration is called as the pollutant volume in 10,000,000 units of air volume. 20 ppm of Sulphur dioxide in air means that 10 mL of SO2 IS present in 10,000,000 mL of air volume.

Mole fraction(X)

Mole fraction is a unit of concentration. In the solution, the relative amount of solute and solvents are measured by the mole fraction. Mole fraction is calculated by dividing the number of moles of a component from total number of moles in a solution.

X(A) = moles of A / total moles.


From the above information we have learnt that the methods for expressing concentrations in volumetric analysis. Also, we can define what is normality and molarity, and also the preparation of various solution concentrations in terms of normality and molarity.

Frequently asked questions

What are the 5 ways of expressing concentrations of solution?

Methods of expressing concentration of solution includes percentage by weight, percentage by volume, weight by volume, mole fraction, parts per million, molarity and etc.

What is the most common way of expressing concentration?

Percent concentration by mass or percent by volume of solute in a solution is the common way of expressing concentration.

What is the unit of concentration?

The quantitative units of concentration include molarity, molality, mass percentage, parts per thousand, parts per million (ppm), parts per billion.

What is the SI unit of volume?

Cubic meter is the SI unit of volume.

What is the symbol for concentration?

Symbol for concentration is C.

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