Chemical Engineering Tips – Chemical Formulas

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A formula that represents the composition of a substance using element symbols is called a chemical formula. Chemical formulas include empirical formulas, molecular formulas, structural formulas, empirical formulas, electron formulas, etc. Empirical formula. A formula that uses element symbols to represent the types of elements that make up a compound molecule and their atomic ratios in the simplest integer proportions is commonly referred to as the simplest formula. For example, the simplest formula for acetylene and benzene is both CH, while the simplest formula for ethylene and its homologs is CH2. For some substances, their simplest formula is also their molecular formula, such as water (H2O), methane (CH4), sulfur dioxide (SO2), etc. Molecular formula. A formula that represents the composition of a pure element or compound molecule using element symbols. The molecular formula has multiple meanings. Taking NH3 as an example: it denotes the substance ammonia; it indicates that ammonia is composed of nitrogen and hydrogen elements; it represents one molecule of ammonia or 1 mol of ammonia; it shows that one ammonia molecule contains 1 nitrogen atom and 3 hydrogen atoms; it indicates that the mass ratio of nitrogen to hydrogen in an ammonia molecule is 14:3, with a mass percentage composition of 82.4% nitrogen and 17.6% hydrogen; it shows that the molecular weight of ammonia is 17, and its molar mass is 17 g/mol. For gaseous substances, the molecular formula also indicates that the molar volume of the gas under standard conditions is 22.4 L/mol. Structural formula. A short line is used to represent a covalent bond, connecting the element symbols to show the arrangement of atoms in a molecule. For example, the structural formula of acetic acid is a schematic representation. It represents a simplified structural formula of the functional groups contained in an organic compound molecule, also known as a structural shorthand; for example, the empirical formulas for acetic acid and alcohol are CH3COOH and C2H5OH respectively.