Dilutions

• Dilution is the process of changing the concentration of a solution by adding additional solvent to a solution

  • You may want to adjust dilutions for certain materials to make them work better in experiments

• Can be calculated with​ the following equation

  • M₁*V₁ = M₂*V₂

    • M₁= Original Molarity

    • V₁= Original Volume

    • M₂= Diluted Molarity

    • V₂=Diluted Volume​

Dilutions Practice Problem

• 53.4 mL of a 1.50 M solution of NaCl is on hand, but you need some 0.800 M solution. How many mL of 0.800 M can you make?

  • M₁=​ 1.50 M

  • V₁=53.4

  • M₂=0.8 M

  • V₂=?

Solubility and Polarity

• Solubility is the ability of two compounds to form a solution

  • "Like Dissolves Like"​

    • Polar Compounds dissolve in Polar Compounds, while non-polar compounds dissolve non-polar compounds​

  • Miscible: Two compounds can dissolve

    • Can be sped up by shaking/stirring the mixture to break up droplets and increase surface area

  • Immiscible: Two Compounds can't dissolve

    • Tend to form layers

Solubilities of Solid Compounds

• Dissolving can only occur at surfaces where the solute and solvent touch

  • Breaking up solids into smaller pieces helps the process

• Solubility increases with Temperatures

Saturation

• There are limits to how much of a solute can be dissolved in an amount of a solvent

• Saturated Solution: A solution that contains the maximum amount of solute​

  • Any additional solute just​ collects at the bottom

• Unsaturated Solutions: Contain less than the maximum amount of solute

• Supersaturated solutions: Contain more than the maximum amount of a solute possible due to special circumstances

  • Primarily Temperature changes​

Gas Solubility

• Gases dissolve in liquids

• Gases have a low attraction between molecules

  • Think of a bottle of Soda, do you see a lot of bubbles before the bottle is opened?

    • Opening the bottle changes the pressure, reducing the solubility of CO₂ ​

• Henry's Law: the solubility of a gas increases as the partial pressure on the gas increases

• Temperature decreases gas solubility

  • This is why soda goes flat​ when warm

Physical Properties of Solutions

• Electrical Conductivity-Depends on whether a substance contains charged particles that are able to move

  • ​Pure, Distilled water does not conduct electricity, but ionic solutions do

  • Electrolytes: Substances that dissolve in a liquid solvent and provide ions that conduct electricity

    • Ions: an element that has either lost or gained an electron and has a charge

    • Two Types

      • Strong Electrolytes: completely dissociate into ions and conduct electricity well

      • Weak Electrolytes: Provide few ions solutions and do not conduct Electricity well

Colligative Properties

• Colligative Properties-Properties that are determined by the number of particles in a system, but are not dependent of the properties of the particles themselves

  • Solutes can change the colligative properties of the solvents they are in

    • Example: Salt lowers the freezing point of water and raises the boiling point of water

  • Any Solute has contributes to the colligative properties of the solution

• Higher Concentrations of solutes have a greater change than lower concentrations