Solutions part 2: Dilutions, Solubility, and Saturation

Solutions part 2: Dilutions, Solubility, And Saturation

By Abby Fancsali

Fill in the Blank

Review: Determine the Molarity of a solution prepared by dissolving 16.9 g NaOH in enough water to make 250.0 mL of solution.

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=?

Fill in the Blank

Solve for V₂: (1.50 mol/L) (53.4 mL) = (0.800 mol/L) (V₂) Round to Two Decimal Places

Fill in the Blank

If you dilute 175 mL of a 1.6 M solution of LiCl to 1.0 L, determine the new concentration of the solution.

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

Multiple Choice

Which Word describes two substances that can not Dissolve

• A solution

• Miscible

• Immiscible

• Dilution

Multiple Choice

What will dissolve Faster?

• Salt grains

• Rock Salt

• A Salt Block

• They will all Dissolve at the same rate

Multiple Choice

Which of the Following can you add more solute to and have it dissolve without changing the properties of the solution?

• A Saturated Solution

• An unsaturated Solution

• A Super Saturated Solution

Multiple Choice

What do you expect to conduct Electricity the best

• Pure Water

• A Strong Electrolyte

• A Weak Electrolyte

• They all Conduct the same