Reactions in Chemistry The Basics of Chemical Equations

What is a chemical equation? Chemical equations are just quick ways of communicating information about a chemical reaction that could take place. Chemical equations can tell you: ▫What chemicals undergo a reaction (reactants) ▫What new chemicals are formed during the reaction (products) ▫What conditions are necessary for the reaction to take place (heat, catalysts, light) ▫The states of matter of the reactants and products ▫The direction in which the reaction will proceed

Important Symbols

Basic Equation Setups

How many types of equations are there? Chemical equations can come in different forms: ▫Word equations – equations that involve words, rather than formulas, to describe what is reacting and what is produced. ▫Skeleton equations – show formulas for reactants and products in place of their names. ▫Chemical equations – begin with skeleton equations and provide more information about the reaction, such as states of reactants and products or necessary conditions for the reaction to take place, like adding heat, light, or requiring the presence of a catalyst (something to speed up a reaction, although it doesn’t get used up in the process)

Example: If given the following reaction to describe: When methane gas burns, it combines with oxygen to form carbon dioxide and water. ▫Word equation – methane + oxygen  carbon dioxide + water ▫Skeleton equation – CH 4 + O 2  CO 2 + H 2 O ▫Chemical equation – CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O (l)

Problem 1 Hydrochloric acid and solid sodium hydrogen carbonate will react to form aqueous sodium chloride, water and carbon dioxide gas. ▫Word equation – ▫Skeleton equation – ▫Chemical equation –

Problem 2 Hydrogen peroxide solution will break down in the presence of light into water and oxygen gas. ▫Word equation – ▫Skeleton equation – ▫Chemical equation –

Demo: Problem 3 A piece of aluminum foil is put into copper (II) chloride solution. What evidence of chemical change do you see? The products are aluminum chloride and copper. ▫Word equation – ▫Skeleton equation – ▫Chemical equation –