Which of the following is not a decomposition reaction? This question often puzzles students in chemistry classes, as decomposition reactions are a fundamental concept in understanding chemical transformations. In this article, we will explore the characteristics of decomposition reactions and identify the option that does not fit the definition.
Decomposition reactions are chemical processes in which a single compound breaks down into two or more simpler substances. These reactions are typically represented by the general equation: AB → A + B. The substances formed in a decomposition reaction are usually elements or simpler compounds. Now, let’s examine the options and determine which one does not qualify as a decomposition reaction.
Option A: 2H₂O → 2H₂ + O₂
This reaction is a classic example of a decomposition reaction. Water (H₂O) breaks down into hydrogen gas (H₂) and oxygen gas (O₂). Therefore, option A is a decomposition reaction.
Option B: 2KClO₃ → 2KCl + 3O₂
This reaction also fits the definition of a decomposition reaction. Potassium chlorate (KClO₃) decomposes into potassium chloride (KCl) and oxygen gas (O₂). Hence, option B is a decomposition reaction.
Option C: 2H₂ + O₂ → 2H₂O
This reaction is not a decomposition reaction. Instead, it is a combination reaction, where two elements (hydrogen and oxygen) combine to form a compound (water). Therefore, option C is the correct answer to the question.
Option D: CaCO₃ → CaO + CO₂
This reaction is another example of a decomposition reaction. Calcium carbonate (CaCO₃) breaks down into calcium oxide (CaO) and carbon dioxide (CO₂). Thus, option D is a decomposition reaction.
In conclusion, the correct answer to the question “Which of the following is not a decomposition reaction?” is option C: 2H₂ + O₂ → 2H₂O. This reaction is a combination reaction, not a decomposition reaction. Understanding the differences between these two types of reactions is crucial for students to grasp the fundamentals of chemical transformations.
