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Concentration of Solution

Amount of constituents (solute) present in a solution is called concentration. Concentration is used to describe the composition of a solution quantitatively. Concentration is described in the following ways:

(i) Mass percentage (w/w):

Mass % of component = Solutions class 12 chemistry concentration1

(ii) Volume percentage (%) (v/v):

Volume percentage (%) of component = Solutions class 12 chemistry concentration2

(iii) Mass by volume percentage (%) (w/v)

Mass of solute dissolved in 100ml of solution.

Mass of by volume percentage (%) to describe concentration is used generally in medicine and pharmacy.

(iv) Parts per million (ppm):

Parts per million = Solutions class 12 chemistry concentration3

Parts per million is used to describe the concentration when solute is present in trace (very small) quantities.

(v) Mole fraction:

Mole fraction of component (x) = Solutions class 12 chemistry concentration4

Let in a binary mixture, the number of moles of A and B are Solutions class 12 chemistry concentration5respectively

Therefore,

Solutions class 12 chemistry concentration6 Solutions class 12 chemistry concentration7

Mole fraction of a solution having i number of components

Solutions class 12 chemistry concentration8
Solutions class 12 chemistry concentration9

It is found that sum of all the mole fractions in a given solution is equal to unity (1).

Solutions class 12 chemistry concentration10

(vi) Molarity:

Number of moles of solute per liter of solution is called molarity. It is generally denoted by “ M ”.

Solutions class 12 chemistry concentration11

(vii) Molality:

Number of moles of solute per kg of solvent is called Molality. It is generally denoted by letter “ m ”.

Solutions class 12 chemistry concentration12

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