To convert from the Fahrenheit scale to the Celsius scale the formula is
deg C = 5 ( deg F - 32) / 9.
It has the value 9.648670 X 10^4 coulombs per mole.
This number of coulombs is sometimes treated as a unit of electric charge called the Faraday.
Faraday's Laws of Electrolysis govern the electrolysis of aqueous solutions and state
The simplest laboratory filter for liquids is a fluted
glass funnel in which a cone of special paper, known
as filter paper, is placed. The liquid to be filtered
is passed through the paper filter, whereupon the
insoluble solids are retained on the filter.
Grouch crucibles, which are special containers with
a porous base of sintered glass, are also used as filters.
They are often known as freons. Their use in aerosols is
one cause of the depletion of zone layer.
Fluorspar was described by Agricola in 1530AD, as
fluor (from the Latin fluo, I flow), since it melts at
a red heat, approximately 1330 degC.
Fluorspar is used chiefly as a flux material in the
smelting of iron and steel. It is also used as a
source of fluorine and hydrofluoric acid and in
the manufacture of ceramics and in the optical-glass industry.
Fractional distillation is similar to distillation, but
uses an additional piece of apparatus called a
fractionating column. A fractionating column contains
glass rings or balls which provide a large surface area
for condensation and re-evaporation. The vapour of the
liquid with the lowest boiling point reaches the top of
the column first. Fractional distillation is used to
separate liquids with close boiling points.
Examples of free radical formation include the case
where a chlorine molecule is dissociated by a photon
of light into two chlorine radicals (i.e. unpaired
chlorine atoms), which are highly reactive
These radicals are then available to initiate
and propagate other chemical reactions.
For example, the combustion of alkanes which results in
their complete oxidiation to carbon dioxide and water is
a free radical chain reaction. Although this reaction is
exothermic, a high temperature is required for initiation.
This initial heat is required for the bond breaking which
produces the free radicals that initialise the
reaction. Thereafter, the large amounts of heat
released during the course of the reaction sustains the
reaction. Alkanes can be oxidised completely, by
combustion, to give carbon dioxide and water. For
example, methane burns in air.
Fat
A fat is a triester of glycerol, and on hydrolysis with sodium hydroxide gives glycerol
and Soap (i.e. a mixture
of the sodium salts of the fatty acids).
Fatty Acids
Fatty acids, RCOOH, are a homologous series of organic
acids, where R is an alkyl radical. The higher members
of this series of acids occur in nature in the combined
form of esters of glycerol, and hence all of this
family are called fatty acids.
Feedstock
The Feedstock for the manufacture of petroleum products
and petrochemicals is crude oil extracted from
known reserves.
Fermentation of Carbohydrates
The fermentation of carbohydrates is a form of anaerobic
respiration occurring in certain microorganism (e.g. yeasts),
comprises a series of biochemical reactions by which
sugars (i.e. saccharides), including glucose and
sucrose, are converted to ethanol and carbon dioxide.
Ferric Compound
Ferric compound are compounds of iron in its +3
oxidation state. Examples include iron (III) chloride,
FeCl3, which was previously called ferric chloride.
Ferrous Compounds
Ferrous compounds are compounds of iron in
its +2 oxidation state. Examples include
iron (II) chloride, FeCl2, which was previously
called ferrous chloride.
Ferrous Sulphate
Ferrous sulphate, Fe(II)SO4, is the salt formed when iron is
dissolved in sulphuric acid.
Fertilisers
Fertilisers are the minerals which are added to soil to
increase its productivity in crop production. The major
components of inorganic fertilisers are
Trace levels of other minerals are also often included in
fertilisers, either as trace nutrients for crops or for
uptake by animals grazing on the crops.
Filter
A filter is a device for separating solids from liquids
or an insoluble substance from a soluble one.
Filter Pump
A filter pump is a simple laboratory vacuum pump in which
air is removed from a system by a jet of water forced through
a narrow nozzle. The lowest pressure possible is the vapour
pressure or water.
Filtration
Filtration is a method of separating a solid from a liquid
or an insoluble substance from a soluble one. The mixture
is poured through a filter; the liquid that goes through the
filter and is called the filtrate, and the solid that
remains on the filter is called the residue.
First Law of Thermodynamics
The First Law of Thermodynamics states that in
a system of constant mass, energy can neither be
created nor destroyed, but may be converted from one
form to another.
Flocculation
Flocculation is a process of aggregating into larger
clumps. Finely divided precipitates, where the particles
are small enough to pass through the pores in a
filter, need to undergo flocculation to form larger
particles before filtration.
Fluorescence
Fluorescence is emission of light from compounds which
have been illuminated, due to the return of the compound
from an excited state to the ground state.
Fluorides
Fluorides are the salts of hydrofluoric acid.
Fluorination
Fluorination is a chemical reaction in which a fluorine atom is introduced into a molecule.
Fluorocarbons
Fluorocarbons are compounds obtained by replacing some or
all the hydrogen atoms of hydrocarbons with fluorine atoms.
Their high stability to temperature makes them suitable for
a variety of uses, including aerosol propellants, oils,
polymers, etc..
Fluorspar
Fluorite or fluorspar (i.e. calcium fluoride, CaF2) is
a mineral that occurs in Derbyshire, crystallised in
cubes or octahedral or in compact masses like marble. It
is also called Derbyshire spar, or Blue Jhon, when
the crystals are coloured blue or purple. The
colourless transparent crystals show a bluish tinge when
light falls on them, and this property is
called fluorescence.
Foam
Foam is a dispersion of bubbles of gas in a liquid.
Folic Acid
Folic acid is a member of the vitamin B group of vitamins.
Force
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Formula
A formula is a way of representing a chemical compound
using symbols for the atoms present. Subscripts are used
to denote the numbers of each type of atom.
Fossil Fuels
The fossil fuels (i.e. coal, oil, natural gas, etc.) derive
from the decay of vegetable matter and are used by man as a
source of energy.
Fractional Crystallization
Fractional crystallization is a method of separating a
mixture of soluble solids by dissolving them in a
suitable hot solvent and then lowering the temperature
slowly. The least soluble component will crystallize
out first, leaving the other components in solution. By
controlling the temperature, it is sometimes possible to
remove each component in turn.
Fractional Distillation
Fractionating Column
A fractionating column is added before the condenser
in fractional distillation and contains glass rings or
balls which provide a large surface area for condensation
and re-evaporation.
Frasch Process
The Frasch Process is a method of obtaining sulphur from
underground deposits using a tube consisting of three
concentric pipes. Superheated steam is passed down the
outer pipe to melt the sulphur, which is then forced up
through the intermediate pipe by compressed air from the
inner tube. The steam in the outer casing keeps the
sulphur molten in the pipe.
Free Radical
A Free radical is an atom, or group of atoms, which
normally exist only in combination with other atoms, but
which may exist independently for short periods during the
course of a chemical reaction or for longer periods under
special conditions.
light
Cl2 ==> 2 Cl*
Free Radical Chain Reaction
The free radical chain reaction is the mechanism of many
self-sustaining chemical reactions. Chain reactions are
exothermic (i.e. they release large amounts of heat), but
they may require a high temperature, or other special
conditions, to start them. In the case of
combustion, the initial heat is required for the bond breaking
which is required to produce the free radicals, and
initiate the chain reaction. However, when this initiation has
been achieved, the chain reaction can proceed with the
release of energy in sufficient quantity to continue to propagate
the reaction.
CH4 + 2O2 ==> CO2 + 2H2O + energy
Free Radical Polymerisation
Free radical Polymerisation is one mechanism for the conversion of a large number of small (i.e. low molecular
weight) monomer molecules in to a small number of large (i.e. high molecular weight)
Polymer molecules.
When ethylene is heated under great pressure in the presence of a suitable catalyst a large number of molecules combine together to form polythene (i.e. polyethylene). This reaction takes place by a Free Radical Mechanism, and three distinct stages are involved in the polymerisation process.
H H H H Rad* + C=C ==> Rad C-C*. H H H H
H H H H H H H H Rad C-C* + C=C ==> Rad C-C-C-C* H H H H H H H HAnd, these step is repeated many times to form a long chain hydrocarbon (i.e. polythene). At each step. the chain length grows by two carbon atoms.
Rad (C2H4)n* + C2H4 ==> Rad (C2H4)n+1*
Rad (C2H4)n* + Rad* ==> Rad (C2H4)n Rad
Rad (C2H4)n* + Rad (C2H4)m* ==> Rad (C2H4)n+mRad
Rad (C2H4)n* + Rad (C2H4)m* ==> Rad (C2H4)n-1CH2=CH4) + Rad (C2H4)m-1CH2CH3
n(C2H4) ==> (C2H4)n
Cl2 ==> 2 Cl* (1)
Cl* + CH4 ==> *CH3 + HCl (2)
The methyl free radical then attacks a chlorine molecule to produce a molecule of methyl chloride and to regenerate a chlorine free radical, which proceeds to react as in step (2).
*CH3 + Cl2 ==> CH3Cl + Cl* (3)
Reactions (2) and (3) are repeated until all the methane is depleted.
CH3Cl + Cl* ==> *CH2Cl + HCl (4)
The methyl chloride free radical then attacks a chlorine molecule to produce a molecule of methylene chloride and to regenerate a chlorine free radical, which proceeds to react as in step (4).
*CH2Cl + Cl2 ==> CH2Cl2 + Cl (5)
Reactions (4) and (5) are repeated until all the methyl chloride is depleted.
CH2Cl2 + Cl* ==> *CHCl2 + HCl (6)
The methylene chloride free radical then attacks a chlorine molecule to produce a molecule of chloroform and to regenerate a chlorine free radical, which proceeds to react as in reaction (6).
*CHCl2 + Cl2 ==> CHCl3 + Cl* (7)
Reactions (6) and (7) are repeated until all the methylene
chloride is depleted.
CHCl3 + Cl* ==> *CCl3 + HCl (8)
The chloroform free radical then attacks a chlorine molecule to produce a molecule of carbon tetrachloride and to regenerate a chlorine free radical, which proceeds to react as in reaction (8).
*CCl3 + Cl2 ==> CCl4 + Cl* (9)
Reactions (8) and (9) are repeated until all the chloroform is depleted.
Cl* + *CCl3 ==> CCl4
Cl* + Cl* ==> Cl2
*CCl3 + *CCl3 ==> C2Cl6
The mechanism is an electrophilic substitution. The hydrogen atom which is eliminated must come from the nucleus of an aromatic body, and the halogen atom may be provided either by an aliphatic halogen compound or by an aromatic compound in which the halogen atom is present in a side chain (i.e. not in the nucleus).
For example, when benzene is heated with methyl chloride or bromide in the presence of the catalyst anhydrous aluminum chloride, toluene, CH3.C6H5 (i.e. methyl benzene) is obtained. The catalyst acts as an electron acceptor for a lone pair on the chlorine atom. This polarizes the haloalkane or acyl group.
It is worth noting that the Friedel-Crafts reaction has no parallel in aliphatic chemistry.
For example, any compound containing the carboxyl functional group, -COOH, belongs to the carboxylic acid homologous series and acidic properties are always associated with the carboxylic acids due to the presence of an ionisable hydrogen atom. Some of the common functional groups are illustrated in the accompanying table.
Functional Group General Formula Name of Example
Alcohol R.OHCH3.OH Methanol Aldehyde R.CHOH.CHO Formaldehyde Ketone R.CO.R1CH3.CO.CH3 Acetone Acid R.COOHCH3.COOH Acetic Acid Ester R.COO.R1CH3.COO.C2H5 Ethyl Acetate Amide R.CO.NH2CH3.CO.NH2 Acetamide Amine R.NH2C6H5.NH2 Aniline
It has a five membered ring consisting of four methylene groups, CH2, groups and one oxygen atom.