Solutions

Types of Mixtures

Heterogeneous – unevenly mixed Homogeneous – evenly mixed

Solution Components

Solute – what is being dissolved

Solvent – what is doing the dissolving

May be combinations of gases, liquids, and solids

Suspensions

Particles of solute are too large to stay in solution and settle out unless constantly mixed

Colloids

Particles of solute are small enough to be kept moving by the motion of the solvent particles but big enough to scatter light

EX – fog, mayonnaise Tyndall effect

Electrolytes vs. Nonelectrolytes

Electrolytes dissociate in solution and conduct an electric current

Non-electrolytes do not

Factors Affecting Rate of Solution

1. Temperature

2. Stirring

3. Increasing surface area

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The Solution Process

Factors Affecting the Rate of Dissolution

Increasing surface area

Agitating the solution (stirring)

Heating the solvent

Solubility

There is a limit to how much solute will dissolve in a given amount of solvent

As more solute is added, there is a greater likelihood that solute molecules/ions will collide and recrystalize

Solution equilibrium – the physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates

Unsaturated vs Saturated

A solution that contains the maximum amount of dissolved solute is said to be SATURATED

A solution that contains less solute than a saturated solution under the same conditions is said to be UNSATURATED

Supersaturated Solutions

A solution that contains more dissolved solute than a saturated solution contains under the same conditions is said to be SUPERSATURATED

Solubility Values

The amount of a substance required to form a saturated solution with a specific solvent at a given temperature

“Like Dissolves Like”

Polar solvents can dissolve ionic or polar compounds

Non-polar solvents can dissolve non-polar compounds

Depends on bonding and intermolecular forces between solvent and solute

Liquid Solutes & Solvents

Oil and water are said to be IMMISCIBLE because they cannot dissolve in each other

Liquids that can dissolve each other are said to be MISCIBLE (benzene/carbon tetrachloride or oil/gas)

Pressure Effects on Solubility

Effects mainly gasses

As pressure increases solubility increases

Henry’s Law – the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid

Temperature Effects on Solubility

In general, as temperature increases solubility of solids increase

As temperature increases solubility of gases decreases

Heats of Solution

Change in the amount of heat generated as a solute is SOLVATED (surrounded by solvent molecules)

If ΔH greater than start endothermic

If ΔH less than start exothermic