Stoichiometry

Chapter: Introduction to Stoichiometry

Understanding Basic Terms

  • Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction.

  • A mole is the amount of any substance that contains as many elementary entities as there are atoms in 12 grams of carbon-12.

  • The molar mass of a substance is the mass (in grams) of one mole of that substance.

  • A balanced chemical equation gives us the ratios of the moles of all reactants and products involved in the chemical reaction.

The Mole Concept

  • The mole concept helps us understand the relationship between mass and number of particles in a given sample.

  • The molar mass of an element (g/mol) is numerically equal to the atomic mass of the element (am).

  • The mole concept can be used to convert mass of a substance to the number of moles and vice versa.

Stoichiometric Calculations

  • Stoichiometric calculations involve the calculation of quantities (like mass, volume etc) of reactants or products based on a balanced chemical equation.

  • To perform these calculations, the balanced chemical equation, molar masses of the involved substances and the mass of reactants or products are required.

  • The stoichiometry of a reaction tells us the ratio in which reactants combine to form products.

Limiting Reactants and Excess Reactants

  • The limiting reactant is the reactant that is completely consumed in a reaction and determines when the reaction stops.

  • The excess reactant is the reactant that is left over after the reaction is completed.

Theoretical, Actual and Percent Yields

  • The theoretical yield is the amount of product that can be produced according to the balanced chemical equation from the limiting reagent.

  • The actual yield is the measured or observed amount of product that is obtained from a reaction.

  • The percent yield is the ratio of the actual yield to the theoretical yield, multiplied by 100.

Conservation of Mass in Chemical Reactions

  • The principle of conservation of mass states that in any given chemical reaction, the total mass of reactants is equal to the total mass of products.

  • This principle is fundamental to all stoichiometric calculations.