There can be no progress in science without chemistry. Chemical research is changing in a big way. Chemistry is no longer making a few compounds and studying their properties. We now design new materials with the properties that are desired by us. Some of the important problems faced by humanity can eventually be solved by the use of chemistry.
Chemistry is the study of substances, their makeup and applications. Organic Chemistry, Inorganic Chemistry, Analytical chemistry and Biochemistry are the main branches of chemistry.
Carbon is an important non-metallic element. It is the sixth most abundant element in the universe. It can exist in the free state or in the form of its compounds. It is the major chemical constituent of most organic matter. Carbon is the second most common element in the human body after oxygen. Carbon is present in coal, oil and natural gas.
Electrons are found in regions around the nucleus in an atom. and those regions are called orbitals. The orbitals can be defined and differentiated by size, shape, and orientation. Valence electrons are electrons that are found in the outermost shell. The carbon atom has four valence electrons. These valence electrons are involved in chemical reactions and bonding.
Dissolve a pinch of organic compound in water or alcohol. A few drops of this solution are mixed with neutral ferric chloride solution. If a red, blue or violet colouration appears, then the presence of phenolic group is confirmed.
In an organic compound, unsaturation is due to the presence of double (>C=C<) or triple (–C≡C–) bonds in the molecule. The presence of unsaturation is tested by the following two methods:
Titration of Ferrous Ammonium Sulphate solution against Potassium Permanganate solution
Potassium permanganate is an oxidising agent, both in alkaline and acidic medium. Oxidation is always accompanied by reduction. In this titration, the ferrous ion is oxidised to ferric ion by permanganate ion, [Mn (VII)] and at the same time permanganate ion is reduced to manganese (II) [Mn (II)].
Suppose you are asked to prepare 100 mL 1.0M solution of oxalic acid. As a first step you have to calculate the mass of oxalic acid required for preparing 100 mL of solution.
Volumetric analysis is quantitative analysis in which the results are expressed in a certain definite volume. It involves the use of at least one solution of known strength. It may be prepared by dissolving a definite amount of a solute in a solvent to get a known volume of solution. The volume of this solution which reacts with a volume of the solution of unknown strength of another substance is determined. The process is known as titration.
Proteins are complex nitrogenous organic compounds of high molecular mass. These help in the growth and maintenance of living body and in transmission of genetic information. Proteins are made up of α-amino acids as the basic building blocks. In all, there are 20 different amino acids required by the body. Some of these are called essential amino acids as they cannot be synthesized by the organisms. These must form a part of our food.
Carbohydrates are polyhydroxy aldehydes or ketones and the substances which yield these on hydrolysis. Carbohydrates are classified as:
For detecting the presence of elements in a compound, these have to be converted into ionic forms. This is done by fusing the compound with sodium metal. The elements present in the compound are converted into soluble sodium salts.
Chromatography is a technique by which a mixture of various substances can be separated, purified and identified. The term chromatography is applied to separation processes based on the principle of distribution of a sample between two phases:
Iodoform (CHI3) is the iodine analogue of chloroform. It is a pale yellow crystalline solid (m.p. 119°C), having a characteristic odour. It is used as a mild antiseptic and disinfectant. It is also used in the preparation of many medicinal ointments used as pain-relievers.
Potassium ferric oxalate is an inorganic complex which dissociates in a suitable solvent to give simple potassium (K+) and the complex ferric oxalate, [Fe(C2O4)3]3– ions. In the complex ferricoxalate ion, ferric (Fe3+) ion is linked to three oxalate groups (C2O4)2– through six covalent bonds.
Potash alum is a double salt of potassium sulphate and aluminium sulphate. Hence, it is prepared by taking the amount of K2SO4 and Al2(SO4)3.18H2O in the ratio of their molecular masses, preparing their concentrated solutions separately followed by mixing the concentrated solutions and heating the resulting solution to the crystallization point when white crystals of potash alum (octahedral in shape) are obtained.
Mohr salt is a double salt containing ferrous sulphate and ammonium sulphate in equimolar amounts. Hence, when these two salts are mixed in the ratio of their molecular masses and then a hot saturated solution prepared, filtered and the hot filtrate cooled, light blue or green crystals of Mohr salt (octahedral in shape) are obtained.
A reversible reaction never reaches the completion stage but results in an equilibrium state in which concentrations of all the reactants and products become constant. This equilibrium is dynamic in nature and it is the result of two opposite reactions occurring simultaneously and at the same rate. However, no net change occurs in the system.
Heat is evolved during neutralization of an acid with an alkali. Known quantities of the standard solutions of an acid and alkali are mixed and the change in temperature is noted and from this, the enthalpy of neutralization is calculated.
The EMF of a cell varies with the concentration of the two electrolyte solutions according to the following Nernst equation:
Weak acids and bases do not dissociate completely. An equilibrium exists between the dissociated and un-dissociated molecules.
Solutions of weak acids and bases in water have hydronium ions [H3O+] and hydroxyl ions [OH–] in different concentrations.
The most commonly used acids in laboratories are hydrochloric, sulphuric and nitric acids. The concentration of these commercially available acids are 12M, 18M and 16M respectively. But except a few cases, you need these acids in lower concentrations. The acids in their lower concentrations can be obtained by dilution of concentrated acids.
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