Solutions

Notes

A homogeneous mixture of two or more non-reacting components is called a solution.

A solution consists of:

• Solute: The component present in a smaller amount in a solution.
• Solvent: The component present in a larger amount in a solution.

Example: Alcohol + Water → Solution

• Alcohol (20 mL) = Solute
• Water (60 mL) = Solvent

Important: Every solution is a mixture, but every mixture is not a solution.

2. Classification of Solutions

On the Basis of Number of Components

• Binary Solution: It contains two components, generally one solute and one solvent.
• Multicomponent Solution: It contains more than two components.

The physical state of a solution generally depends upon the physical state of the solvent.

• Solid solvent → Solid solution
• Liquid solvent → Liquid solution
• Gaseous solvent → Gaseous solution

On the Basis of Physical States of Solute and Solvent

1. Solid in Solid → Metal alloy
2. Liquid in Solid → Mercury in silver (Hg in Ag)
3. Gas in Solid → Hydrogen in palladium (H₂ in Pd)
4. Solid in Liquid → Sugar in water
5. Liquid in Liquid → Ethanol in water
6. Gas in Liquid → Oxygen in water
7. Solid in Gas → Camphor in oxygen
8. Liquid in Gas → Chloroform vapour in oxygen
9. Gas in Gas → Oxygen and nitrogen

3. Concentration of a Solution

Concentration describes the relative amount of solute present in a solution.

Mass Percentage (w/w)

\[ \text{Mass Percentage (w/w)} = \frac{\text{Mass of solute}} {\text{Mass of solution}} \times100 \]

Example: Mixing Two NaOH Solutions

20% (w/w) NaOH solution is mixed with 10% (w/w) NaOH solution. Calculate the mass percentage of NaOH in the resultant solution.

Taking 100 g of each solution:

• NaOH in first solution = 20 g
• NaOH in second solution = 10 g
• Total NaOH = 30 g
• Total solution = 200 g

\[ \%\text{NaOH} = \frac{30}{200}\times100 = 15\% \]

Example

300 g of 20% (w/w) NaOH solution is mixed with 200 g of 10% (w/w) NaOH solution.

\[ \text{NaOH from first solution} = \frac{20}{100}\times300 = 60g \]

\[ \text{NaOH from second solution} = \frac{10}{100}\times200 = 20g \]

\[ \%\text{NaOH} = \frac{60+20}{500}\times100 = 16\% \]

4. Parts Per Million (PPM)

The amount of solute present in \(10^6\) parts of solution is expressed as parts per million.

\[ PPM(w/w) = \frac{W_{solute}}{W_{solution}}\times10^6 \]

\[ PPM(v/v) = \frac{V_{solute}}{V_{solution}}\times10^6 \]