Molecular Formula & Molecular Mass

The compounds are the molecules which are identified by common name or scientific name. Scientific name gives the details of its constituent elements. These are represented by molecular formula. For example: O2 is used to represent oxygen. Molecular formula can be written by using the valency of elements with the help of criss-cross method. Molecular formula of a compound represents the number of various atoms present in a molecule and the ratios of the respective masses of the elements present in a compound. It represents molecular mass of a compound. Molecular mass is the sum of atomic masses of all the atomic species present in a molecule. The mass of one molecule of a substance expressed in grams is called the molar mass. Relative molecular mass, commonly known as molecular weight is the sum of all the relative atomic masses of the atoms in a molecule. There are certain rules for writing the name of a compound formed by a metal and non-metal or a compound with two non-metals or with two elements and oxygen. Compounds are also represented by their trivial names. Different compounds react with each other to give a new product. The process that leads to the transformation of one set of chemical substance is known as chemical reaction. The symbolic representation of compounds in a chemical reaction is known as chemical equation. To represent a chemical equation, number of atoms of each element on both sides of the arrow should be equal. This is known as balancing of chemical equation. It is done to follow the law of conservation of matter. Balancing is done by the following two methods: 1. Hit and trial method 2. Partial equation method The balanced reaction with different abbreviated forms of the physical states, aqueous solution and concentration of acids, alkalis etc. are known as informative chemical equation.

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