National League for Nursing (NLN PAX) Practice Exam

Which equation best illustrates a synthesis reaction?

1. 2Na + Cl2 -> 2NaCl

2. NaOH + HCl -> NaCl + H2O

3. 2H2O2 -> 2H2O + O2

4. CH4 + 2O2 -> CO2 + 2H2O

The correct answer is: 2Na + Cl2 -> 2NaCl

A synthesis reaction, also known as a combination reaction, occurs when two or more simpler substances combine to form a more complex product. The equation provided illustrates this type of reaction effectively, as it shows sodium (Na) and chlorine gas (Cl2) coming together to form sodium chloride (NaCl). In this specific reaction, two sodium atoms react with one molecule of chlorine gas, resulting in the formation of two molecules of sodium chloride. This is a straightforward example of a synthesis process, as it involves the direct combination of elemental substances to create a single new compound. The other options present different types of reactions. For example, the reaction of sodium hydroxide with hydrochloric acid demonstrates a neutralization reaction, where an acid reacts with a base to form a salt and water. The breakdown of hydrogen peroxide into water and oxygen is a decomposition reaction, where one compound breaks down into simpler substances. Lastly, the combustion of methane in the presence of oxygen results in the production of carbon dioxide and water, which exemplifies a combustion reaction rather than a synthesis. Hence, the first equation serves as the clearest representation of a synthesis reaction.