Concentration of solution is defined as the amount of solute dissolved in a specific (fixed) amount of solvent.
Often, concentration of solution is described qualitatively, through the use of such words as dilute and concentrated. These are relative terms.
Suppose we have solutions: and with and alcohol in of water each, respectively. In this case, is more dilute than while it is more concentrated than . A solution can be diluted by adding solvent or removing solute. On the other hand, a solution can be concentrated by adding solute or removing solvent.
Molarity is defined as the number of moles of solute per litre of solution:
It is generally represented by .
is dissolved in of solution. What is its molarity?
The molar mass of is . So the number of moles is obtained as follows:
Now, . Hence the molarity is
We have mixed two glucose solution: of and of . What is the molarity of the final solution formed after mixing these two solutions?
We know that
In the first solution, we have
In the second solution, we have
When two solutions are mixed, they will have a total of of glucose, and the final volume is . So the final molarity is
A solution of sulfuric acid has a density of grams per milliliter at What is the molality of the solution?
To simplify the problem, assume you have exactly of solution. Then you have
Normality is defined as the number of gram equivalents per liter of solution:
It is generally represented by
Molarity can be converted to normality by multiplying by valency factor:
What is the normality of a solution?
The -factor of is since sulphuric acid has two replaceable ions.
Since the normality is
Mole fraction for a component is defined as the number of moles of that component per mole of mixture. In a mixture of components, the mole fraction of the component is given by where represents the number of moles of component .
Formality is defined as the number of moles of formula units in one liter of solution. It is used for ionic compounds only: where GFM stands for gram formula mass.
Percentage weight by weight is defined as
Percentage weight by volume is defined as
Percentage volume by volume is defined as
Parts per million (PPM) is defined as
As this concentration unit is generally used for solutions in which the mass of solute is very small as compared to the mass of solution, we can say that this concentration unit is the same as
We will take mass of solute to be , mass of solvent , density of solution , molecular mass of solute , and molecular mass of solvent
So we know that
- g of solute is present in g of solvent, and
- g of solute is present in 1 g of solvent,
which implies g of solute in 1000 g of solvent.
Now, say, assume
- g of solute in g of solution
- g of solute in ml of solution.
Then we have in 1 L of solution, which implies
Here we get the relation guys with derivation. For instance, take the relation between normality (N) and molarity (M) to be
Some of the concentration terms depend on the volume of solution/solvent like molarity and normality. The volume changes as the temperature is varied. Thus, such concentration terms are temperature dependent. On the other hand, terms like molality and mole fraction do not depend on volume, thus being temperature independent. The density is often required to convert temperature independent terms into temperature dependent terms or vice versa.