The concentration of a solution may be defined as the amount of solute present in the given quantity of the solution.

The concentration of solution may be expressed in several ways as discussed below:

Mass Percentage

The mass percentage of a component in a given solution is the mass of the component per 100 g of the solution.

\[\text{Mass percentage of a component = }\frac{\text{Mass of the component in the solution}}{\text{Total mass of the solution}} × 100\]

Volume percentage

In the case of a liquid dissolved in another liquid, it is convenient to express the concentrations in volume percentage. The volume percentage is defined as the volume of the component per 100 parts by the volume of the solution.

Mass by volume percentage (w/v)

Sometimes, we express the concentrations as weight/volume. It is the mass of solute dissolved in 100 mL of the solution

Molarity of a solution

The molarity of a solution is defined as the number of moles of the solute dissolved per litre of the solution.It is represented as ′M′. Mathematically,

\[Molarity = \frac{\text{Moles of solute}}{\text{Volume of the solution (in mL)}} × 1000\]

Molality of the solution

The molality of a solution is defined as the number of moles of the solute dissolved per 1000 g (or 1 kg) of the solvent.

Which of the following statement is correct?

All are correct statements

The correct statements are (1), (2), and (3).

Statement (1) is correct. A molal solution is a solution that contains one mole of solute in 1 kilogram of solvent.

Statement (2) is correct. Molality does not change with temperature because it is a measure of the number of moles of solute per kilogram of solvent, and the mass of the solvent does not change with temperature.

Statement (3) is correct. The unit of molality is mole kg–1.

Therefore, the correct answer is (4) All are correct statements.