An Acid is defined as a substance which contains hydrogen that can be displaced by a metal with the liberation of hydrogen gas and the formation of a salt.
An understanding of the chemical mechanisms that give rise to the properties of acids evolved from a number of different theories of the nature of acids.
An allotrope of an element is one of the forms in which the element can exist.
For example, carbon can exist in several different forms, including graphite and diamond (which are pure forms of carbon that have different crystal structures) and charcoal, coke and lampblack (which are impure forms of carbon that are amorphous).
Sulphur can exist as five different allotropes.
An alloy is a solid solution of one metal in another. It is an example of a mixture, as no chemical bonding exists between the constituent elements in the alloy.
Common examples of alloys include
A number of steels are the important alloys of iron, which include,
An alpha-Particles is the charged particle emitted from the nucleus during its spontaneous decay. It haves the same structure as the nucleus of a helium atom, consisting of two Protons and two Neutrons.
Amides are organic compounds containing the amide functional group (i.e. -C=O.NH2-).
Amides can be regarded as either
Amides are volatile solids.
Amines are organic compounds containing carbon, hydrogen and nitrogen which are derived from ammonia by replacing one or more of the hydrogen atoms by alkyl, alkenyl, alkynyl, or aryl groups. Thus, the amine functional group, -NH2, is contained within the molecule. Amines are classified as
There are significant differences in the reactivities of these amines.
No text prepared for this topic yet
The amount of a substance is measured in moles. One mole is the quantity of the substance (i.e. the weight of the substance in grams) that is present in numerically the same as its molecular weight.
An amphoteric substance is one which has both acidic and basic properties and which can behave as a weak base or a weak acid under different experimental conditions.
Amphoteric oxides are the oxides of weakly electropositive metals. Thus, the oxides of aluminium oxide, zinc oxide, and tin oxide are amphoteric oxides. These amphoteric oxides react as basic oxides with acids and as acidic oxides with bases.
Aluminium oxide reacts with acids
Al2O3 + 6 HCl ==> 2 AlCl3 + 3 H2OAluminium oxide reacts with bases
Al2O3 + 2 NaOH + H2O ==> 2 NaAl(OH)4Water is also an amphoteric oxide
H2O + NH3 <==> NH4(+) + OH(-)
H2O + HCl <==> H3O(+) + Cl(-)
Analysis involves the determination of the composition of a sample.
Qualitative Analysis involves determining the nature of a pure unknown compound or the compounds present in a mixture.
Quantitative Analysis involves measuring the proportions of known components in a mixture, and the chemical techniques include volumetric analysis and gravimetric analysis.
Instrumental Analysis include several physical techniques including spectroscopic techniques, mass spectrometry, polarography, nuclear magnetic resonance, etc.
An anion is the ion which is attracted to the anode. Thus, it is the negatively charged ion.
Anion hydrolysis involves the reaction of the anion of a salt with water to give excess hydroxyl ions in solution.
An anode is the positive electrode in electrolysis experiments, and it is at this electrode that the ions lose electrons. Thus, oxidation reactions occurs at the anode.
Anode reactions are the chemical reactions that occur at the anode of an electrochemical cell, involve the negative ions in solution which migrate to the anode, where they lose an electron and are deposited as neutral atoms.
Anode reactions are oxidation reactions, as they involve the transfer of an electron from the negatively charged ion.
The anti-Markownikoff rule specifies the orientation, in the presence of free radicals, in which an asymmetric molecule adds across the double bond of an alkene in an addition reaction.
The orientation of the addition across the multiple bond in the presence of free radicals is opposite to that specified for ionic reactions in the Markownikoff Rule.
Aqueous solutions are those solutions where water is the solvent. An aqueous solution found in an equation describing a chemical reaction is denoted by the state symbol, (aq).
The arenes are a homologous series of aromatic hydrocarbons, which have a ring structure of six carbon atoms, with alternating single and double bonds. This closed ring structure has a very high stability and these aromatic compounds undergo substitution reactions in order to preserve the configuration of the ring structure.
Argentic compounds are ionic compounds of silver in its higher oxidation state (i.e. +2 oxidation state), Ag(++).
Argentometric titrations are those in which an aqueous solution of silver nitrate is used to quantitatively precipitate a silver halide (e.g. silver chloride, silver bromide) or other insoluble silver salt (e.g. silver thiocyanate) from solution.
Argentous compounds are ionic compounds of silver in its lower oxidation state (i.e. +1 oxidation state) , Ag(+).
Aromatic Compounds are ring compounds with a benzenoid structure (i.e. have a ring structure of six carbon atoms, with alternating single and double bonds), or those resembling benzene in chemical behaviour.
Although aromatic compounds are unsaturated, they do not readily undergo addition reactions, instead undergoing electrophilic substitution to preserve the stability of the aromatic ring.
The simplest aromatic compound is benzene, C6H6.
Aromatic stability is the resistance of aromatic compounds to undergo addition reactions on the ring structure which would destroy the aromatic character (i.e. alternating single and double bonds) of the aromatic ring. Aromatic compounds readily undergo substitution reactions that preserve the aromatic structure of the ring. Aromatic stability is explained by resonance.
The Arrhenius concept of bases regard substance which provides hydroxyl ions as a result of dissociation and ionisation in aqueous solution as being bases.
The Arrhenius concept of neutralisation involves the reaction in which a hydrogen ion and a hydroxide ion combine to form water.
The Arrhenius concept of acids, gave the first understanding of the true nature of acids in aqueous solution.
Arrhenius proposed that acids are substances which give rise to the hydrogen ions in solution and that bases are substances that give rise to hydroxyl ions in solution.
It is the ionisation of the acid which gives rise to these hydrogen ions and thus also gives rise to the acidic properties.
H2SO4 ==> H(+) + HSO4(-)
Atmospheric carbon dioxide results from the combustion of fossil fuels, and it is an important contributor to the greenhouse effect.
Atmospheric Pollution is caused by the emission of substances which are not natural constituents of the air, including soot, smoke, carbon monoxide, hydrocarbons, lead compounds, carbon dioxide, chlorofluorocarbons, sulphur dioxide, and nitrogen oxides.
Soot and smoke, which are particulates released during the combustion of solid fuels, can be controlled by using smokeless solid fuels. The smoke emitted from diesel engines can be controlled by the use of properly adjusted fuel injectors.
Levels of sulphur dioxide can be reduced by using low sulphur fuels.
The quantity of lead compounds which are emitted from petrol engines has been reduced significantly since the introduction of lead-free petrol.
The quantity of carbon monoxide and of hydrocarbons which are emitted from petrol engines can be reduced by using properly adjusting and tuning the engines of cars and by fitting catalytic converters.
International agreements has lead to the reduction of the quantities of chlorofluorocarbons which can be manufactured. Alternative new compounds are being developed to replace the CFCs.