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Exploring Mixtures and their Separation - 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, consisting of a solute and a solvent.

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The component of the solution that is present in larger quantity is called the solvent, while the component dissolved in it is the solute.

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Properties of solutions: Particle size is less than 1 nm1\text{ nm} (10−9 m10^{-9}\text{ m}) in diameter, they do not scatter light (Tyndall effect is absent), and they are stable (solute does not settle).

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A saturated solution is one in which no more solute can be dissolved at a specific temperature. The amount of solute present in a saturated solution at this temperature is its solubility.

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An unsaturated solution contains less than the maximum amount of solute that can be dissolved at that temperature.

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

📐Formulae

Mass of Solution=Mass of Solute+Mass of Solvent\text{Mass of Solution} = \text{Mass of Solute} + \text{Mass of Solvent}

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

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

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

💡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=Mass of solute+Mass of solvent\text{Mass of solution} = \text{Mass of solute} + \text{Mass of solvent} 40+320360\begin{array}{r} 40 \\ + 320 \\ \hline 360 \end{array} Mass of solution = 360 g360\text{ g}. Mass percentage=(40360)×100=40036≈11.1%\text{Mass percentage} = \left( \frac{40}{360} \right) \times 100 = \frac{400}{36} \approx 11.1\%

Explanation:

First, we find the total mass of the solution by adding the solute and solvent. Then, we apply the mass by mass percentage formula.

Problem 2:

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

Solution:

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

Explanation:

The concentration is calculated as the ratio of the mass of the solute to the total mass of the saturated solution, multiplied by 100.