Solutions

Solutions Solutions can be solids, liquids or gases A mixture that appears the same throughout Soluble Capable of being dissolved Solute Substance that is being dissolved Ex. Salt in salt water, Sugar in soda drinks, and Carbon dioxide in soda drinks Solvent Substance that is doing the dissolving Ex. Water in salt water and Water in soda

Solvents at the hardware store

Types Of Solution Gas If the solvent is a gas, gases and liquids are dissolved under a given set of conditions. Ex. Air, oxygen in nitrogen, water in air Liquid If the solvent is a liquid, then gases, liquids, and solids can be dissolved. Ex. Carbonated water, sucrose (table sugar) in water , salt in water forms an electrolyte Solids If the solvent is a solid, then gases, liquids, and solids can be dissolved. Ex. Alloys such as bronze, copper in nickel, mercury in silver and tin

Suspensions and Colloids Suspensions and Colloids are NOT a solution even though they are the same throughout. Suspension The particles in a solvent are so large that they settle out unless the mixture is constantly stirred or agitated The particles in a suspension can be separated from the heterogeneous mixtures by passing the mixture through a filter Examples: Muddy Water, Oil in water, flour in water Colloids Homogeneous mixture with particles that never settles Examples: Fog, clouds, milk, whipped cream

Tyndall Effect Tyndall Effect Scattering of a light beam as it passes through a colloid. colloid solution

Particles In A Solution Ions Particles with a charge Electrolytes Compounds that have a charge and conduct electricity in water Your body uses them in order to maintain nerve impulses and muscle contraction (Na+,Mg2+,K+,Cl-) Nonelectrolytes They do not ionize in water and do not conduct electricity Ex: Sucrose, ethanol, methanol

How Dissolving Happens Water molecules are Polar; they have a positive area and negative area Water molecules cluster around solid molecules, with their negative ends attracted to the positive ends of the solids Water molecules pull substances into a solution The moving water molecules and solid molecules spread out and mix evenly to form a solution

Rate of Dissolving Depends On: Stirring: speeds up dissolving of a solid Temperature: increasing temperature speeds up dissolving Crystal Size: breaking a solid into pieces increases surface area and speeds up dissolving To dissolve a gas into a liquid, COOL the liquid solvent and increase the pressure.

Solubility and Concentration The amount of a substance required to form a saturated solution with a specific amount of solvent at a specified temperature. Solubility depends on the nature of the substances Concentration A concentrated solution has a large amount of solute in the solvent A dilute solution has a small amount of solute in the solvent

Solubility and Concentration cont. Saturated Solution Contains all the solute it can hold at a given temperature As the temperature of the solvent increases so does the amount of solute it can hold Solubility Curve A line on a graph that tells how much solute (saturated solution) can dissolve at any temperature on the graph Unsaturated Solution A solution that is able to dissolve more solute Supersaturated Solution A solution that contains more solute than a saturated solution at the same temperature

Liquid Solutes & Solvents Immiscible Liquid solutes & solvents that are not soluble in each other Example: Bottle of salad dressing Miscible Liquids that dissolve freely in one another in any proportion Intermolecular attraction brings the solvent and solute molecules together. Energy is released in this process.

Effects of Pressure on Solubility Gas + solvent  solution Henry’s law – the solubility of a gas in liquid is directly proportional to the partial pressure of that gas on the surface of the liquid. Effervescence – rapid escape of gas from a liquid.

Effect Of Temperature On Solubility In general as temperature increases the solubility of a gas in liquid decreases. In general as temperature increases the solubility of a solid in liquid increases.

Heat Of Solution Solvated – a solute particle surrounded by solvent particles Formation of solutions can be endothermic or exothermic. Heat of solution – the amount of heat energy absorbed (+) or released (-).

Example 3: What is the solubility of KClO3 at 600C? Example 1: According to the graph above, which substance maintains almost constant solubility over the given temperature range?   Example 2: Which substance decreases in solubility with increasing temperature? Example 3: What is the solubility of KClO3 at 600C? NaCl Ce2(SO4)3 20g

Example 4: A solution containing 50g CaCl2 in 100 g H2O is prepared at 100C. Is the solution saturated, unsaturated or supersaturated?   Example 5: A supersaturated solution at 100C contains 40 g KCl in 100 g H2O. At what temperature was the solution saturated before being cooled to 100C? Example 6: If the supersaturated solution from the previous example is disturbed, how many grams of KCl will suddenly crystallize? unsaturated 400C 10g