Solubility and Solubility Curves

Overview

Solubility:
When a solid solute is placed in a liquid solvent, molecules or ions break away from the solid surface and enter the solvent, creating a uniform solution. The solubility of a substance is the concentration of the solute in a solution at equilibrium with the solid at a specific temperature. It is expressed as the number of grams of solute in 1000g of solvent.

Solubility Curves:
Temperature significantly impacts the solubility of substances, leading to the creation of solubility curves. These curves can be continuous or discontinuous, depending on whether they show sudden changes in solubility or not. Discontinuous solubility curves, like those of Na2SO4·10H2O and CaCl2·6H2O, are a combination of two or more solubility curves, indicating changes in solubility due to factors like the number of molecules of water crystallization.

Questions and Answers

  1. What is the definition of solubility?

    Solubility is defined as the concentration of the solute in the solution when it is in equilibrium with the solid substance at a particular temperature.

  2. How is solubility expressed?

    Solubility is expressed in terms of the number of grams of solute in 1000g of solvent.

  3. What is a saturated solution?

    A saturated solution is a solution in which the rate of dissolution and the rate of crystallization are equal, resulting in a state of dynamic equilibrium.

  4. What are solubility curves?

    Solubility curves are graphical representations showing the variation in solubility of a substance with temperature.

  5. What are continuous solubility curves?

    Continuous solubility curves do not show sharp breaks and exhibit a continuous change in solubility with temperature.

Multiple-Choice Questions

  1. What are the two types of solubility curves?

    a) Linear and Non-linear
    b) Continuous and Discontinuous
    c) Rapid and Gradual
    d) Exothermic and Endothermic
    Answer: b) Continuous and Discontinuous

  2. What technique is used for the separation of impurities from chemical products based on differences in solubility with temperature?

    a) Distillation
    b) Filtration
    c) Fractional Crystallisation
    d) Precipitation
    Answer: c) Fractional Crystallisation

  3. What is the purpose of fractional crystallisation in the context of solubility curves?

    a) To increase solubility
    b) To decrease solubility
    c) To separate impurities from chemical products
    d) To speed up the dissolution process
    Answer: c) To separate impurities from chemical products

  4. Which compound shows exceptional behavior with its solubility decreasing with an increase in temperature?

    a) NaCl
    b) KNO3
    c) CuSO4
    d) Ce2(SO4)3
    Answer: d) Ce2(SO4)3

  5. What is the main factor that causes sudden changes in solubilities leading to discontinuous solubility curves?

    a) Change in pressure
    b) Change in temperature
    c) Change in volume
    d) Change in color
    Answer: b) Change in temperature