Solubility

Solubility

1. Definitions

   • Solute
     • The substance that dissolves in the solvent
   • Solvent
     • the liquid in which the solute dissolves
   • Solution
     • the liquid obtained when the solute dissolves in the solvent
   • Soluble
     • the solute can dissolve in that solvent
   • Insolubles
     • the solute cannot dissolve in the solvent
   • saturation solution
     • no more solute can be dissolves in the solvent at that temperature
   • solubility
     • The no. of grams of solute required to saturate 100g if solvent at a particulat temperature

2. When salt dissolves in water, the particles of salt are broken down and spread out

3. To help solutes that are solids dissolve quicker

   • add more water
   • stir
   • heat it
   • crush

4. If a solid is continually added to cold water , even with plenty of stirring eventually no more will dissolve and there will be some undissolved solute at the bottom of the beaker.

   • the solution is said to be saturated

5. increase temperature of the solution and keep adding solid then more will dissolve until the solution becomes saturated again

6. decrease the temperature of the hot saturated solution then some of the solid will come out of the solution

   • this is called crystallisation

7. for solids in General

   • If a solid is soluble in a liquid, it usually gets more soluble as the temperature incleases

8. For gases in general

   • If a gas is soluble in a liquid, it usually gets less soluble as the temperature increases

9. Aquatic life such as snails and fish depend on the amount of oxygen dissolved in water

   • Some power stations use water as a coolant and may return warm water into a river
     • This makes the amount of dissolved oxygen in the river decreases
       • Aquatic life will die if the oxygen level goes too low

10. Two methods of determining solubility

    • by evaporation
    • by crystallisation

11. Finding the solubility of Sodium chloride by the method of evaporation

    • apparatus
      • Stage 1
      • Stage 2
    • Method
      • 1. add salt to boiling water
      • 2.Filter off excess salt
      • 3.evaporate of water so cyrstallisation

12. to work out solubility

    • solubility= Mass of Solute/Mass of Solvent x 100

13. Finding the solubility of potassium chlorate by the method of crystallisation

    • Aparatus
      • part A
      • Part B
    • Method
      • 1. Measure out 2g of potassium chlorate into a boiling tube and add 4 cm3 of water
      • 2. Set up the apparatus as shown in part A
      • 3. Heat the mixture until all the crystals have dissolved
      • 4. Set up part B, Stir the solution continually, and note the temperature at which the crystals first appear
      • 5. Repeat the experiment several more times, using 4cm3 more water each time

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