In how many ways can the concentration of a solution be expressed?
(a) 1
(b) 3
(c) 5
(d) 8
The correct answer and explanation is :
The correct answer is: (c) 5
Explanation:
The concentration of a solution refers to the amount of solute present in a given quantity of solvent or solution. It can be expressed in various ways depending on the context and the required precision in scientific or industrial processes. There are five major ways to express concentration:
1. Mass Percent (w/w%)
- This expresses the mass of the solute divided by the total mass of the solution, multiplied by 100.
- Formula:
[
\text{Mass percent} = \left( \frac{\text{Mass of solute}}{\text{Mass of solution}} \right) \times 100
] - Common in industrial formulations and household products.
2. Volume Percent (v/v%)
- This is used when both solute and solvent are liquids.
- Formula:
[
\text{Volume percent} = \left( \frac{\text{Volume of solute}}{\text{Volume of solution}} \right) \times 100
] - Frequently used in alcohol content labeling.
3. Mass/Volume Percent (w/v%)
- It describes the mass of solute per 100 mL of solution.
- Formula:
[
\text{Mass/Volume percent} = \left( \frac{\text{Mass of solute (g)}}{\text{Volume of solution (mL)}} \right) \times 100
] - Widely used in pharmaceuticals and biological labs.
4. Molarity (M)
- Defined as moles of solute per liter of solution.
- Formula:
[
\text{Molarity} = \frac{\text{Moles of solute}}{\text{Liters of solution}}
] - Common in chemistry labs and reactions involving stoichiometry.
5. Molality (m)
- Defined as moles of solute per kilogram of solvent.
- Formula:
[
\text{Molality} = \frac{\text{Moles of solute}}{\text{Kilograms of solvent}}
] - Used when temperature changes occur, as it is temperature-independent.
These five methods cover most of the standard ways concentration is reported in chemistry. Each has its specific use depending on the experimental or industrial requirement.