Percentage and Molecular Formula
Percentage and Molecular Formula If we know the percentage composition of the elements in an organic compound we can find out its formula but formulae are of three types: (a) Empirical or simple formula. (b) Molecular formula. (c) Structural formula. Empirical formula “The empirical formula of compound is the simplest formula deduced from its percentage composition showing its composition by mass. It represents the relative number of atoms of each atom present in a molecule of the compound” The empirical formula of...
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Quantitative analysis : 1. Estimation of Carbon and Hydrogen: Both carbon and hydrogen are estimated together in one operation. A known mass of the organic substance is burnt in excess of oxygen when the carbon and hydrogen present in it are oxidised to carbon dioxide and water respectively. The mass of and thus formed are determined and the percentage of carbon and hydrogen is calculated. The method is known as Liebig’s combustion method. Apparatus: The apparatus used consists of three...
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Qualitative analysis: After purifying an organic compound, the first step in establishing its composition is to ascertain the nature of the elements present in it. The order of abundance in which these elements are present in organic compounds is indicated below: Element Order of abundance Carbon Always...
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Chromatography Chromatography is an analytical technique employed for the purification and separation of organic and inorganic substances. It is also very helpful for the fractionation of complex mixtures, separation of closely related compounds such as isomers, homologues as well as in the isolation of unstable compounds. In this technique the compounds are recovered without any change or alteration. Classification: Chromatography can be classified into following types: (1) Paper Chromatography (2) Column Chromatography (3) ...
read moreCriteria of Purity of a Substance
Criteria of Purity of a Substance The melting point and boiling point of a substance indicates the purity of a substance. Every pure compound has a definite melting point or boiling point. If the substance melts at lower temperature or boils at a higher temperature then it is impure. The impurities depress the melting point and elevate the boiling point. Melting Point: The pure solid substance melts sharply at a definite temperature while as impure substance will have a lower and indefinite melting point. In the laboratory it is...
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Purification of Organic Compounds Most of the organic substances when synthetically prepared or isolated from natural source are impure due to the presence of some bye-products or reactants. Before the compound can be analysed qualitatively or quantitatively, it is necessary that it should be in a pure state. Purification is not always easy and various methods depending upon the nature of the compound and impurities are employed. The following methods are generally used for this purpose: (1) Crystallization (2) Fractional...
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