Solutions

Solution- A homogeneous mixture of two or more substances Solute: What gets dissolved Solvent: What does the dissolving (greater amount) Insoluble: solute cannot dissolve in solvent What is a homogenous mixture. Salt/water Sand/water Water is usually a solvent Water =universal solvent Solvent in you body Insoluble= chalk dust

Types of Solutions Solids (alloys) Liquids Gas Brass: copper and tin Sterling silver: silver and copper Liquids Antifreeze: water and ethylene glycol “Alcohol”: ethanol and water Gas Air: nitrogen and oxygen Car exhaust: carbon dioxide, carbon monoxide, various oxides of nitrogen Solid solns. Silver alone is too soft so must combine with some copper to harden. Liquids: liquid w liquid ethylene glycol toxic tasts sweet Etoh type you drink but there other kinds Gas:car exaust is homogeneous not all gas soln are clear. Nitrogen trioxide is orange also nitrogen dioxide.

Types of solutions (cont) Aqueous Means (Latin) dissolved in water Any solute that may dissolve in water (solvent) The solvent is always water! Hw study terms for homework along with lab.

Factors Affecting Solvation

How a Solution Forms Dissociation – The process of an ionic solid separating into its individual ions Positive ion (cation) is surrounded by the negative side of solvent Negative ion (anion) is surrounded by the positive side of solvent

Examples: NaCl  Na+ + Cl- Mg(NO3)2  Mg2+ + 2NO3- Now you try it! Write the dissociation equation for the following: Ca(OH)2  (NH4)3PO4 

Solvation Interactions between solvent and solute Hydration when solvent is H2O http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/molvie1.swf

Disolving of an Ionic Solid

Factors Affecting Rate of Solvation Surface Area Greater surface area allows for more solvation; therefore faster dissociation The smaller the particles the faster the solute will dissolve Stirring Increases solvation by bringing fresh solvent into contact with surface area of the solute Temperature An increase in temperature increases solvation by causing solvent molecules to move faster

Levels of Saturation Saturated: contains the max amount of solute possible Unsaturated: contains less than the max… Supersaturated: contains more than the max amount possible Still DISSOLVED!

Solubility Definition: the amount of solute that dissociates in a given solvent under specific conditions Conditions: Nature of materials Temperature Pressure (gases only)

Nature of Materials Like dissolves like Solute Polar Solvent Nonpolar Solvent polar soluble insoluble nonpolar ionic

Temperature Liquid and Solid in liquid: Gas in liquid: The higher the temperature of the solvent the more solute it can hold dissolved. Gas in liquid: The higher the temperature of the solvent the less solute it can hold dissolved. Note that level of saturations is dependent on temperature.

Solubility is temperature dependent

For gases, level of saturation is dependent on temperature too

Check for Understanding The doctor recommends you gargle with salt water. Will more salt dissolve in cold or warm water? You saturate hot water with NaNO3. What will happen when it cools? Certain fish (i.e. trout) require a lot of dissolved oxygen to live. Will they live in cool or warm streams? Challenge: You have a beaker of water saturated with NaCl and NaNO3. How could you use their differences in solubility to separate them?

Pressure Only a significant factor for a gas in a liquid The greater the pressure – the more solute can be held

Check for Understanding You want to keep your carbonated beverage from going flat. Name two things you can do. Which factor will not only cause a solute to dissolve faster but usually results in more solute being able to be dissolved?