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Is Matter Around Us Pure - Solutions

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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A solution is a homogeneous mixture of two or more substances. It consists of a solvent (the component that dissolves the other component) and a solute (the component that is dissolved).

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The particles of a solution are smaller than 1 nm1\text{ nm} (10−9 m10^{-9}\text{ m}) in diameter. Therefore, they cannot be seen by naked eyes.

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Because of very small particle size, they do not scatter a beam of light passing through the solution. So, the Tyndall effect is not observed in true solutions.

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A solution is stable; the solute particles do not settle down when left undisturbed.

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A Saturated Solution is a solution in which no more solute can be dissolved at a specific temperature. If the amount of solute is less than the saturation level, it is called an Unsaturated Solution.

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Solubility is the maximum amount of a solute that can be dissolved in 100 g100\text{ g} of a solvent at a specified temperature.

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Concentration of a solution is the amount of solute present in a given amount (mass or volume) of solution.

📐Formulae

Mass by mass percentage of a solution=Mass of soluteMass of solution×100\text{Mass by mass percentage of a solution} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100

Mass by volume percentage of a solution=Mass of soluteVolume of solution×100\text{Mass by volume percentage of a solution} = \frac{\text{Mass of solute}}{\text{Volume of solution}} \times 100

Volume by volume percentage of a solution=Volume of soluteVolume of solution×100\text{Volume by volume percentage of a solution} = \frac{\text{Volume of solute}}{\text{Volume of solution}} \times 100

Mass of solution=Mass of solute+Mass of solvent\text{Mass of solution} = \text{Mass of solute} + \text{Mass of solvent}

💡Examples

Problem 1:

A solution contains 40 g40\text{ g} of common salt in 320 g320\text{ g} of water. Calculate the concentration in terms of mass by mass percentage of the solution.

Solution:

Mass of solute (salt) = 40 g40\text{ g}. Mass of solvent (water) = 320 g320\text{ g}. Mass of solution = 40 g+320 g=360 g40\text{ g} + 320\text{ g} = 360\text{ g}. Mass percentage=(40360)×100=11.1%\text{Mass percentage} = (\frac{40}{360}) \times 100 = 11.1\%.

Explanation:

First, find the total mass of the solution by adding the mass of the solute and the solvent. Then, divide the mass of the solute by the total mass of the solution and multiply by 100100 to get the percentage.

Problem 2:

To make a saturated solution, 36 g36\text{ g} of sodium chloride (NaClNaCl) is dissolved in 100 g100\text{ g} of water at 293 K293\text{ K}. Find its concentration at this temperature.

Solution:

Mass of solute (NaClNaCl) = 36 g36\text{ g}. Mass of solvent (H2OH_2O) = 100 g100\text{ g}. Mass of solution = 36 g+100 g=136 g36\text{ g} + 100\text{ g} = 136\text{ g}. Concentration (mass/mass %)=(36136)×100≈26.47%\text{Concentration (mass/mass \%)} = (\frac{36}{136}) \times 100 \approx 26.47\%.

Explanation:

The concentration is calculated based on the total mass of the solution (solute + solvent) at the given temperature of 293 K293\text{ K}.