Presentation on theme: "Solutions. Parts of Solutions b Solution- b Solution- homogeneous mixture. b Solute b Solute- what gets dissolved. b Solvent b Solvent- what does the."— Presentation transcript:
Parts of Solutions b Solution- b Solution- homogeneous mixture. b Solute b Solute- what gets dissolved. b Solvent b Solvent- what does the dissolving. b Soluble b Soluble- Can be dissolved.
Aqueous solutions b b Dissolved in water. b b Water is a good solvent because the molecules are polar. b b The oxygen atoms have a partial negative charge. b b The hydrogen atoms have a partial positive charge.
Hydration b b The process of breaking the ions of salts apart. b b Ions have charges and attract the opposite charges on the water molecules.
Hydration H H O H H O H H O H H O H H O H H O H H O H H O H H O
Electrolytes b b Electricity is moving charges. b b The ions that are dissolved can move. b b Solutions of ionic compounds can conduct electricity and b electrolytes b are called electrolytes. Solutions are classified three ways.
Types of solutions b Strong electrolytes b Strong electrolytes- completely dissociate (fall apart into ions). b b Many ions- Conduct well. b Weak electrolytes b Weak electrolytes- Partially fall apart into ions. b b Few ions -Conduct electricity slightly. b Non-electrolytes b Non-electrolytes- Don’t fall apart. b b No ions- Don’t conduct.
Making solutions b b What solute and the solvent are determines Whether a substance will dissolve. How much will dissolve. b b A solid substance dissolves faster if- It is stirred or shaken. The particles are made smaller. The temperature is increased.
How Much? b Solubility b Solubility- The maximum amount of substance that will dissolve at that temperature (usually g/L). b Saturated solution b Saturated solution- Contains the maximum amount of solid dissolved. b Unsaturated solution b Unsaturated solution- Can dissolve more solute. b Supersaturated- b Supersaturated- A solution that is temporarily holding more than it can, a seed crystal will make it come out; forms a precipitate
Liquids b Miscible b Miscible means the that to liquids can dissolve in each other. b Immiscible b Immiscible means they can’t
What affects solubility? b b Temperature b b Pressure b b The polarity of the solvent polar and ionic compounds dissolve in polar solvents such as water non-polar solutes dissolve in non-polar solvents such as alcohol
What affects solubility? b b For solids in liquids as the temperature goes up the solubility goes up. b b For gases in a liquid as the temperature goes up the solubility goes down. b b For gases in a liquid- as the pressure goes up the solubility goes up.
The Solubilities of Several Solids as a Function of Temperature While most substances become more soluble in water with increased Temperature, sodium sulfate and cerium sulfate do not
Pressure b b Changing the pressure doesn’t effect the amount of solid or liquid that dissolves b b They are incompressible. b b However, it does effect gases.
Dissolving Gases b b Pressure effects the amount of gas that can dissolve in a liquid. b b The dissolved gas is at equilibrium with the gas above the liquid.
Gases are predictable b b As temperature increases, solubility decreases. b b Gas molecules can move fast enough to escape.
b b The gas is at equilibrium with the dissolved gas in this solution. b b The equilibrium is dynamic.
b b If you increase the pressure the gas molecules dissolve faster. b b The equilibrium is disturbed.
b b The system reaches a new equilibrium with more gas dissolved.
Concentration b b A measure of the amount of solute dissolved in a certain amount of solvent. b b Concentrated solution has a large amount of solute. b b Dilute solution has a small amount of solute. b b Expressed as g/L. b b But chemical reactions don’t happen in grams
Molarity b b The number of moles of solute in 1 Liter of the solution. b b M = moles/Liter b b What is the molarity of a solution with 2.0 moles of NaCl in 4.0 Liters of solution. b b.50 mol/L
Making solutions b b Pour in a small amount of solvent b b Then add the solute and dissolve it b b Then fill to final volume. b b M x L = moles b b How many moles of NaCl are needed to make 6.0 L of a 0.75 M NaCl solution? b b 4.5 mol
Dilution b b The number of moles of solute doesn’t change if you add more solvent. b b The moles before = the moles after b b M 1 x V 1 = M 2 x V 2 b b M 1 and V 1 are the starting concentration and volume. b b M 2 and V 2 are the final concentration and volume. b b Stock solutions are pre-made to known M.