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Solvent, Solute, Solutions and Solubility

Solvent, Solute, Solutions and Solubility. Solutions. All solutions consist of 2 parts Solvent (the substance that does the dissolving, makes up the majority of the solution – usually liquid, but can also be solid or gas)

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Solvent, Solute, Solutions and Solubility

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  1. Solvent, Solute, Solutions and Solubility

  2. Solutions • All solutions consist of 2 parts • Solvent (the substance that does the dissolving, makes up the majority of the solution – usually liquid, but can also be solid or gas) • Solute (the substance that dissolves – can be solid, liquid or gas) Solvent Solution Solute A solution is formed when a solute dissolves in a solvent

  3. Liquid solutions at rtp – Solvent = Water? • Usually, we use water as a solvent because many substances can dissolve readily in it. • However, the solvent does not have to be water! • Substances that do not dissolve in water may be soluble in other solvents • E.g. ethanol (an alcohol), oil.. We shall focus mainly on aqueous solutions

  4. Solvent : Water Solute : Chlorine gas • Chlorine • Greenish-yellow gas • Low melting and boiling point • Poor electrical conductor Chlorine is used in bleaches for our clothes.

  5. Solvent : Ethanol Solute : Iodine Iodine is a non-metallic element that sublimes when heated to form a violet vapour. When dissolved in ethanol, it forms tincture of iodine, used as an antiseptic. Uses: antiseptic

  6. Is a solution a.. • Element? • Compound? • Mixture? Mixture! No fixed proportion of solute / solvent required

  7. Solubility • The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature • (units: g / 100 g) • Copper(II) sulfate has a solubility of 32 g /100 g in water (at 20°C)

  8. Describing solutions • Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C) • 100 g of water (100 ml) • 2 g of copper(II) sulfate • 30 g of copper(II) sulfate • 32 g of copper(II) sulfate • 35 g of copper(II) sulfate Dilute solution Concentrated solution Saturated solution Suspension

  9. Factors affecting solubility? • Type of solute • e.g. copper(II) sulfate / salt / sugar • Type of solvent • e.g. water / ethanol • Temperature of solvent • Generally, solubility  as temperature  • Pressure of surroundings • Generally, solubility  as pressure 

  10. Suspension? 35 g 100 g Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C) The amount of substance present is over its solubility limit

  11. Suspension? The substance does not dissolve in the solvent

  12. Common errors.. X • Clear solution? • Transparent solution? • Colourless solution! • Cloudy solution? • White colour solution? • Milky solution? • Suspension! (White precipitate in a colourless solution) X X X X

  13. Rate of dissolving

  14. Rate of dissolving is NOT solubility! • Recall: • Rate of dissolving: How fast it dissolves • The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature

  15. Making solutions quickly • Assumption: The amount of solute used is << solubility limit • Factors affecting rate of dissolving • Temperature of solvent • Particle size of solute • Stirring

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