Which equation represents a decomposition reaction?

• A. 2Na + Cl2 -> 2NaCl
• B. NaOH + HCl -> NaCl + H2O
• C. 2H2O2 -> 2H2O + O2
• D. CH4 + 2O2 -> CO2 + 2H2O

Answer: (C)

A decomposition reaction is when a single compound breaks apart into two or more simpler substances. The clue is one reactant producing multiple products.

The equation 2H2O2 -> 2H2O + O2 fits this pattern: a single substance, hydrogen peroxide, splits into water and oxygen gas. This is exactly what a decomposition reaction looks like, often requiring energy input or a catalyst to break the bonds.

The other examples involve different types of reactions: forming a compound from two reactants (synthesis), an acid-base neutralization, or a hydrocarbon reacting with oxygen to produce carbon dioxide and water (combustion), which starts with more than one reactant and/or does not break a single compound into parts.