# Solutions

## Concentration of Solutions:

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 =

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

Volume percentage (%) of component =

## (iii) Mass by volume percentage (%) (m/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 =

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) =

Let in a binary mixture, the number of moles of A and B are respectively

Therefore,

Mole fraction of a solution having i number of components

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

## (vi) Molarity:

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

## (vii) Molality:

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

Topics covered in this chapter of Solutions

1. Solutions

2. Types of Solutions

3. Solutions - Concentration

4. Solution of NCERT In Text Questions

Class 12 Biology

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