Coarse dispersion systems ✅ Flashcards
What is a dispersion system?
A system consisting of two or more phases.
1) the dispersed phase
2) the dispersed medium, continuous phase
What type of dispersion do heterogenous mixtures undergo?
coarse dispersion and colloidal dispersion
size > 100nm / size 1-100nm
What type of disperse systems do homogenous mixtures undergo?
molecular dispersion
size < 1nm
What are some features of molecular dispersion?
- cannot be filtered through filter paper
- cannot be seen with a naked eye
What are some features of coarse dispersion?
- easily filtered with filter paper (filtration)
- relatively fast sedimentation (caused by gravity or other forces)
What is suspension? How is dispersion achieved?
heterogenous fluid containing solid particles that are sufficiently large for sedimentation.
- dispersion is made by mechanical agitation (eg. sand in water)
What is emulsion?
suspention of liquid droplets (dispersed phase) of a certain size within a second immiscible liquid (continuous phase).
What are the two types of emulsion classifications?
1) Oil in Water (O/W)
2) Water in Oil (W/O)
What is an oil in water emulsification?
oil droplets dispersed in water (eg. milk)
What is a water in oil emulsification?
water droplects dispersed in oil (butter)
What is a colooidal dispersion?
a system in which particles of colloidal size (1-100nm) if any state are dispersed in a continuous phase of a different state.
What are colloids?
- a homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance.
- colloids include gels, sols, and emulsions;
- the particles do not settle,
- particles cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
a substance of gelatinous consistency.
What is the difference between a colloid and a crystalloid?
colloid- substances that do not diffuse through a semipermeable membrane
crystalloid- substances which do diffuse and are in true solution
What are the three classifications of colloids?
1) lyophilic colloids
2) lyophobic colloids
3) associated colloids
What are lyophobic colloids?
solvent ‘hating’
- mixed with a suitable liquid, very weak force of attraction,
- difficult to prepare
- less stable
- IRREVERSIBLE IN NATURE
What are lyophillic colloids?
solvent ‘loving’ colloids
- mixed with a suitable liquid, high force of attraction,
- stable solution
- do not precipitate
- eg. gums, starch and proteins
exception:
- addition of very high amounts of electrolytes may cause precipitation
- addition of excessive liquid: regain original state
REVERSIBLE IN NATURE
What is coagulation?
the instability of a colloidal solution.
How can coagulation occur?
- heating
- increasing concenration
- adding electrolytes
- adding another colloid (oppositely charged particles)
How are lyophobic solutions prepared?
1) condensation method
2) dispersion method
What are the different condensation methods?
chemical:
1) by oxidation (bubbling oxygen through solution)
2) by reduction
3) by hydrolysis
physical:
1) exchange of solvent
2) excessive cooling
What are the different dispersion methods?
1) mechanical dispersion
2) peptisation (adding of electrolyte)
What are the properties of colloids?
physical:
1) heterogenous nature
2) stable nature
3) filterability
mechanical:
1) brownian movement (always move)
2) diffusion
3) sedimentation
optical:
1) tyndall effect (scattering of light)
What is a micelle?
- colloidal shized particle formed by the association of molecules having a hydrophobic tail and hydrophillic head.
- electrically neutral
- contains:
a) nucleus
b) 2 layers of ions (as the shell) - absorb ions
What is a colloid called in which the dispersed phase consists of micelles?
association colloid
What is the layer of ions closer to the nucleus called in micelles?
the adsorption layer
What is the layer of ions further from the nucleus called in micelles?
the diffusion layer
{m[Fe(OH)3] * nFeO+ * (n-x)Cl- x+ * xCl-}
What is:
1) {m[Fe(OH)3] * nFeO+ * (n-x)Cl- x+ * xCl-}
2) m[Fe(OH)3]
3) nFeO+ * (n-x)Cl- x+
4) xCl-
5) {m[Fe(OH)3] * nFeO+ * (n-x)Cl- x+
1) micelle
2) nucleus
3) adsorption layer
4) diffusion layer
5) granule
What is a true solution? What is a solute? What is a solvent?
homogenous mixture of 2+ substances
- cannot be seen with a naked eye
- cannot be filtered
solute: component that is dissolved
solvent: dissolving agent (most abundant component in solution
What is typically the solvent?
1) the substance which determines the state of the finished solution
2) the solution which is present in th ehighest concentrations
How are solutions classified according to electrical conductivity?
1) electrolytes (conducting substance)
2) non-electrolytes (non-conducting substance)
What are miscible liquids? What are immiscible liquids?
Miscible- completely soluble (solute and sovent are both polar or non polar)
Immiscible- insoluble (one of solute and sovent is polar and teh other is non polar)
What affects solubility?
1) nature of the solvent (electronegativity, polarity, asymetry)
2) temperature (increase = increase)
3) pressure (increase = increase)
What is a saturated solution?
solution containing the maximum quantity of solute that dissolves at a certain temperature.
rate of dissolving = rate of crystalization
What is an usaturated solution?
solution containing less than the maximum quantity of solute that dissolves at a certain temperature.
What is an supersaturated solution?
solution containing more than the maximum quantity of solute that dissolves at a certain temperature.
- very unstable
- warming solvent will dissolve more
What factors affect the rate of solubility?
- particle size (smaller = faster)
- temperature (higher = faster)
- concentration of solution (higher concentratin = slower rate)
- agitation/stirring (more = faster)
What is a concentration of a solution? dilute? concentrated?
amount of solute dissolved in a giver quantity of solvent/solution.
dilute- small amount of solute
concentrated- large amount of solute
How to calculate the mass percent solution?
mass of component / total mass of solution * 100%
What is molarity?
the number of moles of solute per liter of solution.
m= mol of solute/l of solvent
What is the molar fraction?
the ratio of the number of moles to the total number of moles of all components present.
the sum of all mole fractions must equal to 1!
How many grams of sodium carbonate (Na2CO3) do we need if one wants to prepare 1.5l (1500ml) of 0.3N solution?
Cn=M/(EV)
E=M/(n* V)
T=Cn*E/1000
Calculate the titer of phosphoric acid (H3PO4) solution if one knows that Cn=0.25 N gE/L.
T=CnE/1000
E=MH2PO4/31=32.65
3*1
What is normality concentration (Cn) of calcium hydroxide if 40ml of 0.1N of acetic acid (Ca(OH)2 was used to titrate 80 ml of Ca(OH)2 solution
