7. Solutions And Colloids Flashcards
Homogeneous mixture/ Solution
-mixture uniform throughout molecular level
-air, sea
-all gas mixtures are homogeneous
-homogeneous solid mixture: alloy
Heterogeneous mixture
-distinct regions separated from each other by well-defined boundaries
-most solid mixture are heterogeneous
Alloy
-i.e. brass, steel
-melting solids ➡️ mixing molten components ➡️ allowing misture to solidify
Most common types of solutions
•Gas in liquid- carbonated water
•Liquid in liquid- wine
•Solid in liquid- salt water (saline soln)
•Gas in has- air
•Solid in solid- 14-carat gold
Properties of solution
- Distribution of particles is uniform
-every part of solution has exactly same composition and properties - Components of a solution do not separate on standing
- Solution cannot be separated into its components by filtration
- For any given solute and solvent, it is possible to make solutions of many different compositions
- Solutions are almost always transparent/clear (except solid solutions)
- Solutions can be separated into pure components (distillation, chromatography)
Acid rain
-raindrops contain CO2, O2, N2, SO2
CO2 + H2O ➡️ H2CO3 (carbonic acid)
SO2 + H2O ➡️ H2SO3 (sulfurous acid)
SO3 + H2O ➡️ H2SO4 (sulfuric acid)
Smelting
-melting or fusing an ore as part of separation process
-produces soluble gases
-acid rain
Solubility
-maximum amount of solid that will dissolve in a given amount of a particular solvent at a given temperature
-physical constant like melting point and boilinf point
Insoluble solids
-very low solubility in particular solvent
Soluble solids
-high solubility on particular solvent
Ethanol and water
-miscible in all proportions
-form solution no matter what quantities of each are mixed
Saturated solution
-solvent contains all the solute it can hold at a given temperature
Unsaturated solution
-solution containing lesser amount of solute than maximum
Supersaturated solution
-solution that contains more than the equilibrium amount of solute at a given temperature and pressure
Factors affecting solubility
1. Nature of solvent and solute
-polar compounds dissolve in polar solvents
-nonpolar compounds dissolve in nonpolar solvents
Factors affecting solubility
2. Temperature
-for most solids and liquids,
⬆️ Temperature ⬆️ Solubility (i.e. Glycerine, NaCl in water)
•exemptions: Li2SO4 in water
-for gases
⬆️ Temperature ⬇️ Solubility
Seeding
-molecules need a seed (surface on which to begin crystallizing) to precipitate
-addition of crystal of the solute to solution to provide surface onto whuch solute molecules can converge
Factors affecting solubility
3. Pressure
-little effect on solubility of liquids and solids
-for gases ⬆️ Pressure ⬆️ Solubility in a liquid
Henry’s law
-The solubility of a gas in a liquid is directly proportional to the pressure
-explains why carbonated beverage foams when it is opened
•bottle sealed under greater than 1 atm of pressure
•when opened at 1 atm, pressure decreases, solubility decreases
•excess CO2 is released, forming bubbles
Concentration
-amount of solute dissolved in a given quantity of solvent
Common units of concentration
1. Percent concentration
% w solute / v solvent
% w / w
% v / v
Common units of concentration
2. Molarity
M = moles solute / volume solution
Common units of concentration
3. Dilution
-only solvent is added in dilution
-moles of solute remain unchanged
M1V1 = M2V2
Common units of concentration
4. Parts per million
-for very dilute solution
ppm = (g solute / g solvent) x 10^6
ppb = (g solute / g solvent) x 10^9
Hydrated (for water only) or solvated ions
-when the combined force of attraction to solvent molecules is greater than the ionic bond of the crystal
-ions removed from crystals is surrounded by solvent molecules ,(solvated)
Water of hydration
Water molecules in a crystal
Hydrates
-Substances that contain water in their crystals
i.e. Gypsum CaSO4.2H2O
Plaster of Paris (CaSO4)2.H2O