# SI units of expressing concentration of solutions

The concentration of a solution is expressed by following methods:

1. Percentage

The volume or weight (concentration) of some solute is expressed in the percentage. For example 10 gin of sodium chloride is added in 90 gm of water. It is called 10% solution.

1. Molarity

The number of moles of a solute per liter of a solution is called molarity. One mole of any substance is equal to its molecular weight. A gram molecular weight of a substance is dissolved in water to make exactly one liter of solution at 20 °C. It called a molar solution (M). For example, the molecular weight of sucrose is 342.3. A molar (I M) solution of sucrose contains 342.3 grams of sucrose. It is dissolved in one liter of the solution. It becomes one molar solution.

The solutions expressed in terms of molarity can be diluted arithmetically.

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1. Molality

The number of moles of a substance dissolved in 1000 cm3 of solution is called molality. Gram molecular weight of a substance is dissolved in 1000 cc of water. It produces molal solution.