A chemical equation is a symbolic representation of a chemical reaction. It shows the reactants (starting materials) and products (resulting substances), typically separated by an arrow (→). The coefficients in front of each substance indicate the relative amounts of reactants and products.
To write a balanced chemical equation, you must adjust the coefficients so that the number of atoms of each element is equal on both sides of the equation. This is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.
There are several common types of chemical reactions:
Stoichiometry is the quantitative study of reactants and products in a balanced chemical equation. It allows us to predict the amounts of substances consumed or produced in a reaction.
The mole (mol) is the SI unit for amount of substance. It is defined as the number of carbon atoms in exactly 12 grams of carbon-12. One mole of any substance contains Avogadro's number (6.022 × 10²³) of particles (atoms, molecules, or formula units).
The molar mass of a substance is the mass of one mole of that substance, expressed in grams per mole (g/mol). It can be calculated by summing the atomic masses of all the atoms in the chemical formula.
Percent composition is the mass percentage of each element in a compound. Empirical formulas represent the simplest whole-number ratio of atoms in a compound, while molecular formulas show the actual number of atoms of each element in a molecule.
In a reaction, the limiting reactant is the reactant that is completely consumed first and limits the amount of product formed. The amount of product calculated based on the limiting reactant is the theoretical yield. The actual yield is the amount of product obtained experimentally. The percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage.
Practice exercises for this week's lesson will be provided in a separate file.