# Concentration of Solution and their Units | Chemistry Grade XI

### Concentration of Solution # Concentration of Solution and their Units

Concentration of solution
Concentration of solution can be defined as the amount of solute present on a definite quantity of solution. The solution whose strength or concentration is known, the solution is known as a standard solution and the solution whose concentration is unknown is called an unknown solution. The concentration of the solution is expressed in different terms or units and they are as follows;

1. Percentage: It can be defined as the amount of solute in gram present in 100ml or 100gm solution. The amount of solute in gram present in 100ml solution is called percent by volume. Similarly, the amount of solute in gram present in 100gm solution is called percent by mass.
Percent by volume = (wt of solute in gram / wt of solution in ml) * 100
Percent by mass = (wt of solute in gram / wt of solution in gram) * 100
For example; 10 percent of NaCl  solution  by volume means that 10gm NaCl is present in 100ml NaCL solution.

2. Gram litre: It is amount of solute in grams present in one-litre solution.
Gram per litre = ( weight of solute in gram / Volume of solution in ml) * 1000.

3. Molarity: Number of mole (gram molecular weight ) present in one litre of solution is called molarity. It is denoted by ‘M’.
Molarity(M) = (No. of mole / Volume of solution in ml) * 1000
= (Weight of solute in gram / Molecular weight ) * (1 / volume of solution in ml) * 1000
= Gram per litre / Molecular weight

4. Molality: The numbers of gram molecular weight (mole) dissolve in 1000gm (1 kg) solvent is called molality. It is denoted by ‘m’.
Molality = (no. of grams molecular weight / Wt. of solvent in gram) * 1000

5. Normality (N): The number of gram equivalent weight present in 1-litre solution is known as normality. It is denoted by ‘N’.
Normality = (no. of gram equivalent weight / volume of solution in ml) * 1000

6. Mole fraction: Mole fraction of solute can be defined as the ratio of number of mole of solute to the total number of mole of solute and solvent present in the solution. It is denoted by ‘X’.

X= N/ (Na + Nb)
Xb = Nb / (Na + Nb)
Here, X= mole fraction of solute
N= no. of moles of solute
N= no. of moles of solvent

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