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The Amazing World of Solutes, Solvents, and Solutions - How Much Solute Can a Fixed Amount of Solvent Dissolve?

Grade 8CBSE

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 solute and a solvent.

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Solute: The substance that is dissolved in a solvent (usually present in smaller quantity).

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Solvent: The medium in which the solute is dissolved (usually present in larger quantity).

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Saturated Solution: A solution in which no more solute can be dissolved at a specific temperature. If you add more solute, it will settle at the bottom.

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Unsaturated Solution: A solution in which more solute can be dissolved at the same temperature.

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Solubility: The maximum amount of solute (in grams) that can be dissolved in 100 g100\text{ g} of a solvent at a particular temperature is called its solubility.

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Effect of Temperature: Generally, the solubility of solids in liquids increases with an increase in temperature.

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

📐Formulae

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

Concentration (Mass by Mass %)=(Mass of SoluteMass of Solution)×100\text{Concentration (Mass by Mass \%)} = \left( \frac{\text{Mass of Solute}}{\text{Mass of Solution}} \right) \times 100

Concentration (Mass by Volume %)=(Mass of SoluteVolume of Solution)×100\text{Concentration (Mass by Volume \%)} = \left( \frac{\text{Mass 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 g\text{Mass of solute (salt)} = 40\text{ g} Mass of solvent (water)=320 g\text{Mass of solvent (water)} = 320\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 percentage=(40360)×100=11.1%\text{Mass percentage} = \left( \frac{40}{360} \right) \times 100 = 11.1\%

Explanation:

First, we find the total mass of the solution by adding the mass of the solute and the 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 g\text{Mass of Solute} = 36\text{ g} Mass of Solvent=100 g\text{Mass of Solvent} = 100\text{ g} Total Mass of Solution=36+100=136 g\text{Total Mass of Solution} = 36 + 100 = 136\text{ g} Concentration=36136×100≈26.47%\text{Concentration} = \frac{36}{136} \times 100 \approx 26.47\%

Explanation:

In a saturated solution, the amount of solute is its solubility at that temperature. The concentration is calculated relative to the total mass of the solution (136 g136\text{ g}).