Introduction to Compounds or Molecules in Chemistry
Organic compounds are the chemistry of carbon compounds or molecules. This definition includes classes of compounds such as carbon monoxide, carbon dioxide, carbonates, and carbon disulfide as the organic molecules but they are examples of inorganic chemical substances. Hence the difference between organic and inorganic substances is very complicated in chemical science. Therefore, to define differentiation, an organic molecule is the substance produced from living organisms and the inorganic molecule is the substance that was not prepared from environmental living organisms.
Although the list of organic compounds such as sugar, starch, alcohol, resins, indigo, methane, ethylene, etc known from the earliest times but the formula and chemical reactions of these compounds unknown in chemistry. But very little progress in their chemistry courses until about the beginning of the eighteen century.
In 1675, Lemery published a famous science journal, Cours de Chemie in chem, and divided organic chemical substances from natural sources into three classes.
- Organic compounds from mineral
- Compounds from plant namely vegetables
- Organic molecule from the animal
Organic Molecule in Chemistry
This definition accepted but very quickly in science by Lavoisier in 1784 classified organic compound or molecule on the help of its origin in chemistry. All compounds obtained from vegetable and the animal sources always contain at least carbon and the hydrogen atom, and frequently, nitrogen, oxygen, and phosphorus. He showing the close relationship between vegetable and animal products. Therefore, the Lavoisier’s unit work stimulated further research topics in the same direction that led to modify Lemery’s classification.
Due to the improvement of the analytical techniques, some cases the same compounds obtained from these two sources. This led to the reclassification of organic compounds into two classes
- All those which would be obtained from vegetables or animals. Thus these substances produced by living organisms.
- All those substances which not prepared from a living organism.
Science goes step by step with revel the new information of atom and molecule. But the modification of rules and classifications of compounds also changed. In 1828 Wohler converted ammonium cyanate into urea, a substance obtained from animal sources. This weekend the distinction between organic and inorganic chemical elements. But the previous definition of organic molecule completely ended with the synthesis of acetic acid from its component chemical elements by Kolbe in 1845.
Therefore, we can define organic chemistry is the study of carbon compounds. But this definition no longer enjoyed because it includes CO2, CO, CS2 molecule, etc, since these are the kingdom of inorganic chemistry. Hence organic substance is the hydrocarbon or the derivatives of hydrocarbon.
Chemical Formula of Substances
The empirical formula in chemistry indicates the relative number of each class of atom in the general molecule and help to calculate from the percentage composition of the compound.
Question: If 0.202 gm of an organic compound gave on combustion 0.361 gm of carbon dioxide and 0.147 gm of water. What is the empirical formula of this organic compounds?
Weight of carbon = (12/44) × 0.361 gm
= 0.0985 gm
Weight of the hydrogen = (2/18) × 0.147
= 0.0163 gm
Hence the weight of oxygen
= 0.202 – (0.0985 + 0.0163)
= 0.0872 gm
Therefore, the weight of carbon, hydrogen, and oxygen by their respective molecular mass and ratio of atoms are
C : H : O
= (0.0985/12) : (0.0163/1) : (0.0872/16)
= 3 : 5.98 : 2
Thus the weight of carbon, hydrogen, and oxygen by their respective molar mass and the ratio of atoms are
C : H : O
= (0.0985/12) : (0.0163/1) : (0.0872/16)
= 3 : 5.98 : 2
Thus the of this empirical formula of the organic substance is C3H6O2.
Chemical formula Analysis in Chemistry
% of carbon
= (0.0985/0.202) × 100
= 48.76 %
But the % of hydrogen
= (0.0163/0.202) × 100
= 8.07 %
If the percentage of carbon and hydrogen can be evaluated and oxygen obtained by subtraction of thair sum 100.
% of oxygen
= 100 – (48.76 + 8.07)
= 43.17 %
Molar Mass Analysis in Chemistry
The molecular formula in chemistry gives the actual number of atoms of each class in the inorganic or organic molecules obtained by multiplying some whole number in the empirical formula. But this whole number obtained from the consideration of the molar mass. But in many cases, the whole number is one. Therefore, the standard physical methods for the analysis of organic and inorganic compounds are
- Vapour density
- The elevation of boiling point
- Depression of freezing point
These standard methods in chemistry help mainly for the general class of molecules. But other physical analyses used for a high molar mass.
- Graham’s law of diffusion
- Rate of sedimentation of molecules
- The viscosity of liquid and gases
- The osmotic pressure formula of gas molecules
- X-ray radiation analysis for organic compounds
- Mass and atomic spectrum of molecules
Introduction to Physical Science
Physical chemistry is the help for the study of general physical properties, principle, and application of principle on atom or molecules of the matter. Therefore, in this part of science, we study the physical properties of amorphous and crystal solid, liquid and ideal and real gas molecule, the principle of chemical and ionic equilibrium, the law of conservation of energy in thermodynamics, heat capacity, thermo-chemistry, colligative properties of matter, phase rule and phase diagram, chemical kinetics and behavior of properties of the catalyst, etc. But the study of physical chemistry is incomplete if the student confines himself only the theoretical discussion. He must gain the practical significance of the theory and various problems.
Introduction to Analytical Chemistry
Analytical chemistry concern with the determination of the chemical composition of matter. However, modern analytical chemistry help for identified general substances that determines its structure and analysis of its composition and class of reactions. Therefore the most difficult task for an analytical chemist is to explain what is analytical chemistry? It is an interdisciplinary domain of science where a large number of research topics contributed to its development.
Therefore all chromatographic methods invented by biochemist or biological scientists, while methods of the electromagnetic spectrum and mass spectroscopy discovered by physicists. But if we close look at the number of reach topics published in different journals uses the analytical methods for his research. Although 60% of such chemistry papers are published by persons who are not analytical chemists in true sense.