Meaning of Stoichiometry (What is it, Concept and Definition)

What is Stoichiometry:

Stoichiometry is the calculation for a balanced chemical equation that will determine the proportions between reagents and products in a chemical reaction.

The balance in the chemical equation obeys Dalton's conservation principles and atomic models, such as the Mass Conservation Law, which stipulates that:

the mass of the reagents=The mass of the products

In this sense, the equation must have equal weight on both sides of the equation.

Stoichiometric calculations

stoichiometric calculations is the way in which a chemical equation is balanced.There are 2 ways: the scoring method and the algebraic method.

Stoichiometric calculation by scoring

The scoring method to calculate The stoichiometry of an equation should follow the following steps:

Count the number of atoms of each chemical element in the position of the reagents (left of the equation) and compare those quantities in the elements positioned as products (right of the equation). Balance the metallic elements. Balance the non-metallic elements.

For example, the stoichiometric calculation with the scoring method in the following chemical equation:

CH4 + 2O2 → CO + 2H2O

Carbon is balanced because There is 1 molecule on each side of the equation.Hydrogen also has the same amounts on each side.On the other hand, oxygen adds up to 4 on the left side (reactants or reagents) and only 2, therefore a sub-index 2 is added per trial.to transform CO into CO2.

In this way, the balanced chemical equation in this exercise results: CH4 + 2O2 → CO2 + 2H2O

The numbers that precede the compound, in this case 2 of O2 and 2 for H2O are called stoichiometric coefficients .

Stoichiometric calculation by algebraic method

For the stoichiometry calculation co by the algebraic method the stoichiometric coefficients must be found.To do this, follow the steps:

Assign incognita Multiply the incognita by the number of atoms of each element Assign a value (1 or 2 is recommended) to clear the rest of the unknowns Simplify

See also Catalyst.

Stoichiometric relations

The stoichiometric relations indicate the relative proportions of the chemical substances used to calculate a balanced chemical equation between the reagents and their products of a chemical solution.

The solutions Chemicals have different concentrations between solute and solvent.The calculation of the quantities obeys the principles of conservation and the atomic models that affect the chemical processes.

Principles of conservation

The postulates of conservation principles will later help define atomic models about the nature of Atoms by John Dalton.The models constitute the first theory with scientific bases, marking the beginning of modern chemistry.

Law of conservation of mass : there are no detectable changes in mass total during a chemical reaction.(1783, Lavoisier)

Law of defined proportions : pure compounds always have the same elements in the same mass ratio.(1799, JL Proust)

Dalton's Atomic Models

Dalton's Atomic Models forms the basis of modern chemistry.In 1803, John Dalton's Basic Atomic Theory (1766-1844) postulates what next:

Chemical elements are formed by identical atoms for one element and are different from any other element. Chemical compounds are formed by the combination of a defined quantity of each type of atom that form a molecule of the compound.

In addition, Dalton's law of multiple proportions defines that when 2 chemical elements combine to form 1 compound, there is a relationship of whole numbers between the various masses of an element that combine with a constant mass of another element in the compound.

Therefore, in stoichiometry Cross relations between reactants and products is possible .What is not possible is the mixture of macroscopic units (moles) with microscopic units (atoms, molecules).

Stoichiometry and conversion of units

The Stoichiometry uses as a conversion factor from the microscopic world by units of molecules and atoms, for example, N2 indicating 2 molecules of N2 and 2 atoms of Nitrogen to the macroscopic world by the molar relationship between the amounts of reagents and products expressed in moles.

In this sense, the N2 molecule at the microscopic level has a molar ratio that is expressed as 6.022 * 1023 (one mole) of N2 molecules.

See also Molar mass.