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
Anhydrous crystals
-crystals without water
Hygroscopic substance
-substance able to absorb water vapor from air
Electrolytes
-substances that conduct electric current when dissolved in water or when in molten state
-i.e. NaCl
Cathode
Negative electrode where cations migrate
Anode
-positive cathode where anions migrate
Non-electrolytes
-substances that do not conduct electricity
i.e. distilled water
Electric conductance and concentration of ions
⬆️ion concentration ⬆️ electric conductance
Strong electrolyte
-compounds that dissociate completely and conduct electricity
Weak electrolyte
Compounds that dissociate into ions only partially and slighty conduct electricity
Electrolytes in body
-important since it maintains acid-base balance and water balance
•cations: Na+, K+, Ca2+, Mg2+
•anions: HCO3-, Cl-, HPO4^(2-), H2PO4-
Ionic solutions
-can be made from ionic compounds and covalent compounds as long as it is completely converted to ions in dilute aqueous solution
-conducts current
When will covalent compounds dissolve in water
-if they can form hydrogen bonds eith water, provided that solute molecules are fairly small (no more than 3C atoms for each O,N,F atoms)
-covalent molecules that do not contain O,N,F are almost always insoluble in water (except for rare cases where covalent compound react with water, i.e. HCl)
Importance of water in body
-dissolves ionic substances
-hydrates all polar molecules in body
-serves as vehicle to carry most of organic compounds, nutrients, and fuels as well as waste material
True solution
-maximum diameter of the solute particles is about 1nm
Colloid/ colloidal dispersion/ colloidal system
-diameter of solute particles ranges from 1-1000 nm (large particles)
-particles of this size have very large surface area
-stable (i.e. mayonnaise stays emulsified and does not separate into oil and water)
-not filterable by ordinary paper
-borderline homogeneous
Basic characteristics of colloidal system
- Scatter light, appear turbid, cloudy, milky
- Form stable dispersions, do not form separate phases that settle out
Tyndall effect
-light passing through and scattered by a colloid viewed at a right angle
*Light beam
@solution- not visible
@colloid- visible
@suspension- visible
Visible due to light scattering ability of colloid sized particles
Suspensions
-size of colloidal particles is larger than about 1000 nm
-unstable; separate into phases
-filterable with ordinary paper
-transluscent or opaque
Types of colloidal system
Gas in gas- none
Gas in liquid- whipped cream
Gas in solid- marshmallow
Liquid in gas- clouds, fog
Liquid in liquid- mayo, milk
Liquid in solid - cheese, butter
Solid in gas- smoke
Solid in liquid- jelly
Solid in solid- dried paint
Brownian motion
-random, chaotic motion of any colloidal particles suspended in a solvent
Why colloidal particles remain in solution despite all the collisions due to Brownian motion
- SOLVATION LAYER
Most colloidal particles carry a large solvation layer
-colloidal particle is surrounded by solvent molecules which move together with colloidal particle and cushion them; particles do not stick together when colliding - SURFACE CHARGE
Large surface area of colloidal particles acquires charges from the solution; colloidal particles repel each other due to like charges
Solvation layer
-surrounding shell of solvent molecules
Emulsion
-system, such as fat in milk, consisting of a liquid with or without emulsifying agent in an immiscible liquid, usually as droplets larger than colloidal size
Emulsifying agent
-prevents immiscible solute and solvent from separating
-i.e. milk protein casein (oil droplets in milk)
Egg yolk in oil droplets in water
Colligative property
-property of solution that depends only on the number of solute particles and not on the chemical identity of solute
Colligative property
1. Freezing point depression
-the DECREASE in freezing point of a liquid caused by ADDING a solute
-application:
•Use of salts like NaCl and CaCl2 to melt snow in streets (lowers freezing point; mas mahirap ifreeze since need mas malamig)
•Use of antifreeze (i.e. ethylene glycol C2H6O2) in automobile radiators
Colligative property
2. Osmotic pressure
-the amount of external pressure applied to the more concentrated solution to stop the passage of solvent molecules across a semipermeable membrane
Normally, π=i.M.R.T for osmotic pressure
PERO!! if OSMOLARITY hinahanap (osmol unit)
Osmolarity=i.M
Osmotic permeable
Very selective semipermeable membrane that only allows solvent molecules, and nothing else, to pass through
(Small molecules: solvent; large molecules: solute)
Diffusion
-molecules will always diffuse from higher concentration to lower concentration
Osmosis
-passage of solvent molecules from dilute solution to concentrated solution across semipermeable membrane
IMAGINE
May beaker tapos may semipermeable membrane (osmotic membrane) sa gitna
RIGHT PART: Pure water
LEFT PART: Solution (solute with water)
Water moves from dilute to concentrated (right to left) kasi higher concentration of water sa right tapos lower concentration of water sa left (since may solute)
Left side higher level sa right side kasi nag move na yung water molecules, pero hindi pwede masyadong malaki height difference due to gravity
Osmosis stops at unequal level. Level can be made equal if external pressure is applied to higher side
External pressure required: Osmotic pressure
Concentration and osmotic pressure
⬆️ concentration ⬆️ osmotic pressure
Reverse osmosis
-solvent flows from concentrated to dilute solution
-this happens when applied pressure in concentrated solution is GREATER THAN osmotic pressure
-used to make drinkable water from sea water or brackish water
Osmotic pressure in biological organisms
-important since cell membranes are semipermeable; biological fluids must have proper osmolarity
Isotonic
-two solutions with same osmolarity
-used in intravenous (IV) injections
-i.e. red blood cells in plasma; same osmolarity, no osmotic pressure is generated
Hemolysis
-if red blood cells is suspended of distilled water instead of plasma
-rbc: 0.3 osmol; water: 0 osmol
-water flows to rbc; volume of rbc increases and swells
-membrane cannot resist osmotic pressure and rbc eventually burst, spilling contents in water
Hypotonic solutions
-solutions in which osmolarity is lower than that suspended cells
-hypotonic solution will kill rbc by hemolysis
Hypertonic solution
-solution has greater osmolarity than suspended cells
Crenation
- if rbc is placed in hypertonic soln (glucose solution); water flows from cells into glucose solution
-shrivels cells
Dialysis
Process in which a solution containing different sizes is placed in a bag of a semipermeable membrane. The bag is placed into a solvent or solution containing small molecules. The solution in the bag reaches equilibrium with the solvent outside allowing small molecules to diffuse across the membrane but retaining large molecules.
Hemodialysis
-kidney’s main function is to remove toxic waste products
-if not functioning, perform hemodialysis
-patient’s blood circulates through a long tube of cellophane membrane suspended in ISOTONIC SOLUTION and then returns to patient’s vein
-cellophane membrane retains large molecules (i.e. proteins) but allows toxic wastes to pass through
Ionization
Separation of acids and bases into ions
