1. Occasionally a chemical reaction will produce high molecular weight by-product
1. Laboratory manuals have advocated the use of finely powered activated charcoal
for removal of colored impurities.
2. Once crystallization is complete, the crystals must be separated from the ice-cold
mother liquor ( the filtrate)
3. The ability of different column packing to separate two materials of differing
boiling point is evaluated by calculating the number of theoretical plates
4. Although not obvious, the most important variable contributing to a good
fractional distillation is the rate at which the distillation is carried out
5. Azeotropes have constant boiling points that can be either above or … the
boiling points of the individual components
6. Alkanes may either be straight-chain or branched compounds
7. Dinuclear and polynuclear aromatic compounds are present in heavier petroleum
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fractions and residues
The viscosity is the measure of the resistance of a liquid to flow, hence
indicating the “pumpability” of oil
Ash content is an indication of the content of metal and salts present in simple
Salts in crude oil and in heavier products may create seriuos corrosion
problems, especially in the top-tower zone and overhead condensers in
distillation columns
In other to establist a basis for the comparision between different type of crude
oil, it is nescessary to produce experimental data in the form of what is known as
an “assay”
The density level of a crude oil at given boiling point in the curve is a function
of the relative propotions of the main three hydrocacbon series : aromatics,
cycloparafins, parafins, their densities decrease in oder
In the US, crude oils are classified into three types: paraffinic, naphthenic and
asphaltic
By measuring how much of soluties is required to complete the reaction in a
proceduce called titration, the chemist can tell how much of a particular and
chemical is in the solution
Digestion is largely a process of …
Acid rain is a solution of strong mineral acids in water
One of the most important of solvent in their role as media in which chemical
reactions may occur.
Fire and toxicity are major hazards associated with …
Hydrogen bonding is one of the main reasons that some proteins can be put in
water solution or held suspended in water as extremely small particles called
colloidal particles.
20. The molar concentration of a solution is the number of moles of solute dissolved
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in a liter of solution.
………..CO2 …………..suppersaturated
Crystallization is the most important methods for purification of solid organic
compounds.
Crystals can be grown from the molten state just as water is frozen into ices, but
not easy to remove impurities from crystals made in this way.
Most purifications in the laboratory involve dissolving the material to be purified
in the appropriate hot solvent.
Although not obviuos, the most important varible contributing to a good
fractional distillation is the rate at wich the distillation is carried out
A mixture of liquid of a certain definite composition that distill at a constant
temperature without change in composition is call azeotrope
Mearsuring how much of solution is required to complete a reaction is produce
called titration
Digestion is largly a process of breaking down complex, unsloble food
molecules to simple, soluble molecules that may be carried out by the blood to
the body cells.
To make a less concentrated solution from a more concentrated solution is called
dilution
The origins of distillation are lost in antiquity as man in his thirst for more potent
beverages found that dilute solution of alcohol from fermentation could be
separated into alcohol –rich and water-rich portions by heating the solution to
boiling and condensing the vapors above the boiling point liquid – the process of
distillatio
This series of redistillation can be done “automatically” in a fractionating
column.
At equilibrium, vapor containing low boiling material is ascending and high
boiling liqiud is descending through the column.
In the laboratory the successive condensations and distillations that occur in the
bubble cap column take place in a distilling column.
A series of simple distillation take place within a fractionalating column and it is
important that complete equilibrium be attained between the asceding vapors
and the desceding liquid.
It should be an adiabatic process; that is , heat should be stranfered from the
asceding vapor to the descending liquid with no net loss or gain of heat.
When a solution of sugar in water is distilled , the boiling point racorded on a
thermometer located in the vapor phase is 100oC (at 760 torr) through out the
distillation, whereas the temperature of the boiling sugar solution itselt is
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innitally somewhat above 100oC and continue to rise as the concentration of
sugar in the remaining solution increase
The crystals are collected by filtration , the surface of the crystals is washed
with cold solvent to remove the adhering impurities , and then the crystals are
dried
The process of crystallizzation can be broken into 7 discrete steps: choosing the
solvent, dissolving the solute, decolorizzing the solution , removing suspended
solids, crystallizing the solute, collecting and washing the crystals, and drying
the product.
Hydrocarbon solvents such as hexane will dissolve hydrocarbons and other
nonpolar compuonds, and hydroxylic solvents such as water and ethanol will
dissolve polar compounds.
Crystallization is initiated at a point of nucleation – a seed crystal, a speck of
dust, or a scratch on the wall of the test tube if the solution is supersaturated
with the respect to the subtance being crystallized (the solute)
The impurities can be absorbed onto the surface of activated charcoal by
simply boiling the solution with charcoal
On a commercial scale the impurities in brown sugar are absorbed onto charcoal
in the process of refining sugar
Vacumn filtration is not used because the hot solvent will cool during the
process and the product will crystallizze in the filter
The major constituents of most crude oils and its product are hydrocarbon
compuonds, which are made up of hydrogen and carbon only
Hydrodenitrogeneation takes place as well, removing nitrogen as ammonia gas,
thus reducing the nitrogen content to the acceptable limits for feedstocks to
catalytic processes.
Sour crude oil are those containing a high percentage of hydrogen sulfide
Naphta feed to catalytic reformers is hydrotreated to reduce sulfur compuonds to
very low levels to avoid catalyst poisioning.
Crude assay are the systematic compilation of data for the physical properties of
the crude and its fractions, as well as the yield.
The toxixity hazard of solvents arises from absorption through the skin and
inhalation through the lungs. One solvent, dimethyl sulfoxide, is relatively
harmless by itselt but has the property of carrying toxic solutes through the skin
and into the body
The organometallic compuonds are usually concentrated in the heavier fractions
and in crude oil residues
Hydrotreatment may also be used to reduce the metal content in heavy feeds to
catalytic cracking.
... molecules that may be carried out by the blood to the body cells To make a less concentrated solution from a more concentrated solution is called dilution The origins of distillation are lost in antiquity... somewhat above 100oC and continue to rise as the concentration of sugar in the remaining solution increase The crystals are collected by filtration , the surface of the crystals is washed with...20 The molar concentration of a solution is the number of moles of solute dissolved 21 22 23 24 25 26 27 28 29 30 31