Chemical Equations Overview

Overview

This lecture explains how to write chemical equations in both symbolic (formula) and written word formats, and how to translate between the two.

Chemical equations can be written using chemical formulas or as sentences with words.
Chemical formulas use element symbols and may include phase notations (s, l, g, aq).
Word equations describe the reactants and products using full names and phases.

To write a word equation from a chemical formula, name each substance and include its phase.
Example: Na(s) + H₂O(l) → NaOH(aq) + H₂(g) becomes "Solid sodium metal reacts with liquid water to produce aqueous sodium hydroxide and hydrogen gas."
To write a chemical formula from a sentence, identify the reactants and products and translate their names into symbols and phases.
Example: "Solid iron reacts with fluorine gas to produce solid iron(III) fluoride" becomes Fe(s) + F₂(g) → FeF₃(s).

After writing the symbolic equation, compare the number of each atom on both sides.
Adjust coefficients to ensure the same number of each atom on both sides (law of conservation of mass).
Example: Fe(s) + F₂(g) → FeF₃(s) is balanced as 2Fe(s) + 3F₂(g) → 2FeF₃(s).

Chemical Formula — symbolic representation of a substance using element symbols and numbers.
Word Equation — verbal description of a chemical reaction using compound names and phases.
Phase Symbols — indicate physical state: (s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous.
Reactant — substance present before a chemical reaction.
Product — substance formed as a result of a chemical reaction.
Balancing — adjusting coefficients so atoms are equal on both sides of the equation.

Practice translating between word equations and symbolic equations for given reactions.
Review how to balance chemical equations.