Stoichiometry and Calculations Based on Stoichiometry


Stoichiometry is important section of chemistry which expresses the relationship between reactants and products in any chemical reaction which in turn is used for determination of quantitative data. It deals with quantitative calculations based on chemical equation and chemical formulas.

Stoichiometry is derived from the Greek word stoikhein which means element and metron that is stated as to measure. So, stoichiometry is measurement of elements. It is super technical and sounding word which simply demonstrates the use of ratios from balanced equation. Stoichiometric calculations are used to study the chemical reactions and to understand the reasons that why relationship exists between reactants and products and gives an understanding to balance the reactions. In the concept of stoichiometry there are two sub-sections which includes gravimetric analysis and volumetric analysis which are widely used in chemical analysis and testing.

Stoichiometric Coefficients

For a balanced reaction, number of elements are same on both sides of chemical equation. Stoichiometric coefficient is written in front of the atoms, molecules, and ions in chemical reaction so that number of each element can be balanced on both sides of the equation, i.e. reactants and products sides. Stoichiometric coefficients may be whole numbers or fractions, and are preferred and frequently used. These are extremely important as mole ratio is established between the reactants and products. According to the law of conversion of mass, for each of the element in balanced chemical equation, the number of atoms on reactants side should be same as on the product side.

Stoichiometric factors are called as mole ratios and these are based on coefficients in balanced equation and then in turn these are used to relate the moles of a specific reactant to the product. Along with the stochiometric factors, molar masses are used with other factors for the determination of information about one product or reactant in any chemical reaction by using known information about another one.

From balanced chemical equation, stochiometric coefficients helps to get the proportion of reactants and products. The ratios of coefficients can be converted between the amounts of reactants and products in any given chemical reaction.


Stoichiometric Calculations

For stoichiometric calculations, it is essential to understand the relationship that exists between the reactants and products taking part in a chemical reaction. For balanced reaction, number of elements should be equal on both sides of the equation. These stoichiometric calculations are based on the chemical formulas. Formula mass, molar mass, and Avogadro’s number are most widely used calculations in stoichiometry.

All the stoichiometric problems can be easily solved in four basic steps.

  • First of all, convert the units of any given substance into the moles.
  • By using molar ratio, calculate the moles of the substance which is yielded by reaction.
  • Then convert the moles of desired substance to the wanted units.

At first glance, these steps may look like complicated but they become clear with practice.

For reactions occurring in solution, stochiometric calculations quite often use the molarity, or the inverse of molarity as conversion factors. Additionally, it also uses other possible conversion factors.

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