SL Chem - Unit #4: Solutions and Dissolving

Solution

A homogeneous mixture of two or more substance - Same composition throughout the whole mixture (Only one phase)

Binary Solution

Made up of a solvent and solute

Solvent

Substance that is normally in larger quantities and performs the dissolving (the liquid/aqueous solution)

Solute

The substance that is being dissolved in the solvent (normally in smaller amounts than the solvent)

Concentrations

The solute to solvent ratio

Diluted

A solution where there is a relatively smaller amount of solute to solvent

Concentrated

A solution where there is a relatively larger/similar amount of solute to solvent ratio

Aqueous Solution

A solution where the solvent was water

Miscible

Liquids that mix together in any proportion to form a homogeneous solution

Immiscible

When substance that are added together do not form a homogeneous mixture and there are two or more different parts

Dissociation

The dissolving of ionic compounds

• Ions separate from one another and the crystal lattice it was making at first

• Their charges are satisfied by the polar ends of the solvent

Dissolved Ions Create:

1. Hydrated ion

2. Aqueous ions

Factors that Affect Dissolving Rates

1. Particle Size

2. Temperature

3. Stirring

Particle Size as a factor affection dissolving RATES

Smaller particles will dissolve factors compared to larger

• This is because there’s an increased surface area for the solutes that is being exposed to the solvent

Temperature as a factor affection dissolving RATES

Solutes dissolve faster at higher temperatures

• As temperature increases particles begin moving around much quicker allowing for more frequent collision between them 

Stirring as a factor affection dissolving RATES

Agitating the solution increases the dissolving rate

Solvent comes in contact with undissolved solute continually

Different solution saturations

1. Saturard

2. Unsaturated

3. Supersaturated

Saturard solutions

Where an amount of solvent contains the maximum amount of solute that it can dissolve

• At a specific temperature

• When a crystal is placed in an saturated solution its size remains the same

Found on the solubility curve

Unsaturated solution

Where an amount of solvent contains less than it’s maximum amount of solute that could be dissolved 

• At a specific temperature

• When a crystal is placed in an unsaturated solution it gets smaller

Found below the solubility curve

Supersaturated solution

A solution that contains more solute than that that could have been dissolved by the solvent at the given temperature

• UNSTABLE and could create solid crystals until only a saturated solution is left

• When a crystal is placed in a supersaturated solution it gets larger

Found above the solubility curve

Solubility

The measure of the mass of a solute that can dissolve in a specific solvent at certain temperatures

Polarity and it’s affect on solubility

Solutes normally dissolve if they have weak or similar intermolecular forces to the solvent

• Polar solvents will dissolve polar solute (can’t dissolve non-polar)

• Non-polar solvents will dissolve non-polar solutes (can’t dissolve polar)

Molecule Size and it’s affect on solubility

The size of a non-polar/polar portion of a molecule can determine whether it will dissolve in a polar/non-polar solution 

• Eg, if a molecule has a relatively small nonpolar portion to it compared to the size of the polar portion it could still dissolve in a polar solvent, but not a nonpolar one

Temperature and it’s affect on solubility

• Solubility of SOLID SOLUTES normally increase as temperature increases

  • Provides the solvent more kinetic energy and allows for it to break apart much easier

• Solubility of GAS SOLUTE in liquids decreases with a temperature increase

  • Because the gas starts to escape (find a better explanation)

Pressure and it’s affect on solubility

Increased pressure of a gas above a liquid solvent increases the solubility of that particular gas

Solubility Curves

The solubility of a particular substance with temperature changes

Ionic Compounds dissolving

Ions separate from one another and their charges are satisfied by the polar ends of the solvent

• Unless the attraction between the ions is much stronger than that of the solvent so the solute can’t be broken by it

Dissociation Equations

Shows the breaking up of the compound into its ions

• NEVER FORGET STATES

Factors Affecting Ion Solubility:

1. Ion Charge

2. Ion Size

Ion charge affecting ion solubility

As ionic charge increases attraction between ions increases

• So as ionic charge increases solubility decreases

Ion Size affecting ion solubility

Smaller ions contains shorter bonds so the attractive force are strong

• As as ions get smaller their bonds become stronger and solubility decreases

Precipitation Reactions

WHen a solid is formed after two solutions are mixed 

Total Ionic Equations

Shows all of the ions involved → dissolved (aq) compounds are written out as a dissociation while solids stay together (not shown as ions)

• Includes EVERYTHING

Net Ionic Equations

Getting rid of ions that are found on both ends of the reaction and leaving ions that don’t repeat

• Mainly ions that remain dissolved in both the reactants and product get canceled out

• While compounds that started aqueous and then form precipitates are kept in the equation