Stoichiometry Basics

  • Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction.
  • Moles: Fundamental unit in stoichiometry. A mole is 6.02 x 10^23, also known as Avogadro’s number, of any given entities (atoms, molecules, ions etc).
  • Molar mass is the mass in grams of one mole of a substance. It can be calculated by adding up atomic masses of all the atoms in a molecule.

Stoichiometric Calculations

  • Balanced equations: In stoichiometry, calculations are based on balanced chemical equations.
  • Mole Ratio: The coefficients in a balanced equation denote the ratio in which reactants react and products are formed, called the mole ratio.
  • To calculate amount of product formed or reactant needed in a reaction, make use of the mole ratio in the balanced chemical equation.

Limiting Reagent and Excess Reagent

  • Limiting reagent is the reactant that is completely used up in a reaction.
  • Excess reagent is the reactant that remains after the reaction has stopped.
  • The limiting reagent determines the maximum amount of product that can be formed.

Empirical and Molecular Formulas

  • Empirical formula: The simplest, most reduced ratio of atoms within a compound.
  • Molecular formula: The actual ratio of atoms within a compound.
  • The molecular formula can be a multiple of the empirical formula.

Percentage Yield and Atom Economy

  • Percentage yield: A measure of the efficiency of a reaction, calculated by comparing actual yield with theoretical yield.
  • Atom economy: The measure of the amount of reactant atoms that becomes a part of the desired product in intended reaction.